RISC-V: Support debug and float CSR as the unprivileged ones.

RISC-V: Support debug and float CSR as the unprivileged ones.

The unprivileged CSR should be controlled by other specific specs rather
than the privileged spec.  For example, the debug CSR should be controlled
by the debug spec, and the float CSR should be controlled by the float
spec.  User may use assembler options to choose what the debug and other
specs they want, or may encode the versions of specs into the architecture
string directly.  Since we haven't decided which one is better, we set the
defined and aborted versions of unprivileged CSR to PRIV_SPEC_CLASS_NONE
in the include/opcode/riscv-opc.h, to tell assembler don't check priv spec
versions for them.  However, these PRIV_SPEC_CLASS_NONE will be changed
to FLOAT_SPEC_CLASS_* and DEBUG_SPEC_CLASS_* in the future.

	gas/
	* config/tc-riscv.c (riscv_csr_class_check): Removed.  Move the
	checking into riscv_csr_address.
	(riscv_csr_version_check): Likewise.
	(riscv_csr_address): New function.  Return the suitable CSR address
	after checking the ISA dependency and versions.  Issue warnings	if
	we find any conflict and -mcsr-check is set.  CSR_CLASS_F and
	CSR_CLASS_DEBUG are unprivileged CSR for now, so don't check the
	priv spec versions for them.
	(reg_csr_lookup_internal): Call riscv_csr_address to find the
	suitable CSR address.

	* testsuite/gas/riscv/priv-reg-fail-fext.d: Remove -mpriv-spec=1.11.
	* testsuite/gas/riscv/priv-reg-fail-read-only-01.d: Likewise.
	* testsuite/gas/riscv/priv-reg-fail-rv32-only.d: Likewise.
	* testsuite/gas/riscv/priv-reg-fail-fext.l:  We don't care the
	priv spec warnings here.  These warnings are added by accident.
	Remove them and only focus on the ISA dependency warnings.
	* testsuite/gas/riscv/priv-reg-fail-rv32-only.l: Likewise.
	* testsuite/gas/riscv/priv-reg-fail-read-only-01.l: Likewise.
	* testsuite/gas/riscv/priv-reg-fail-version-1p9.l: Updated since
	dscratch0 and dscratch1 are regarded as the unprivileged CSR rather
	than the privileged ones.
	* testsuite/gas/riscv/priv-reg-fail-version-1p9p1.l: Likewise.
	* testsuite/gas/riscv/priv-reg-fail-version-1p10.l: Likewise.
	* testsuite/gas/riscv/priv-reg-fail-version-1p11.l: Likewise.
	* testsuite/gas/riscv/priv-reg.s: Likewise.  Add missing debug CSR.
	* testsuite/gas/riscv/priv-reg-version-1p9.d: Likewise.
	* testsuite/gas/riscv/priv-reg-version-1p9p1.d: Likewise.
	* testsuite/gas/riscv/priv-reg-version-1p10.d: Likewise.
	* testsuite/gas/riscv/priv-reg-version-1p11.d: Likewise.
	* testsuite/gas/riscv/csr-dw-regnums.d: Likewise.
	* testsuite/gas/riscv/csr-dw-regnums.s: Likewise.

	include/
	* opcode/riscv-opc.h: Support the unprivileged CSR.  The versions
	of the unprivileged CSR should be PRIV_SPEC_CLASS_NONE for now.
	* opcode/riscv.h (enum riscv_csr_class): Add CSR_CLASS_DEBUG.

	opcodes/
	* riscv-dis.c (print_insn_args, case 'E'): Updated.  Let the
	unprivileged CSR can also be initialized.