RISC-V: Rewrite the csr testcases.

RISC-V: Rewrite the csr testcases.

Maskray (Fangrui Song) had suggested me before that we should combine
multiple testcases into one file as possible as we can.  So that we can
more easily understand what these test cases are testing, and easier to
maintain.  Therefore, this patch rewrites all csr testcases, to make them
more clean.

gas/
	* testsuite/gas/riscv/csr-fail-nonexistent.d: Renamed from
	priv-reg-fail-nonexistent testcase.
	* testsuite/gas/riscv/csr-fail-nonexistent.: Likewise.
	* testsuite/gas/riscv/csr-fail-nonexistent.s: Likewise.
	* testsuite/gas/riscv/csr-insns-pseudo-noalias.d: Renamed from
	priv-reg-pseudo testcase.
	* testsuite/gas/riscv/csr-insns-pseudo.d: Likewise.
	* testsuite/gas/riscv/csr-insns-pseudo.s: Likewise.
	* testsuite/gas/riscv/csr-insns-read-only.d: Renamed from
	priv-reg-fail-read-only-02 testcase.
	* testsuite/gas/riscv/csr-insns-read-only.l: Likewise.
	* testsuite/gas/riscv/csr-insns-read-only.s: Likewise.
	* testsuite/gas/riscv/h-ext-32.d: Moved hypervisor csrs to csr.s.
	* testsuite/gas/riscv/h-ext-32.s: Likewise.
	* testsuite/gas/riscv/h-ext-64.d: Likewise.
	* testsuite/gas/riscv/h-ext-64.s: Likewise.
	* testsuite/gas/riscv/csr.s: Renamed from priv-reg.s, and then
	added the hypervisor csrs.
	* testsuite/gas/riscv/csr-version-1p9p1.d: The csr testcase when
	the privileged spec is 1.9.1.  Also tested all invalid csr warnings
	when -mcsr-check is enabled.
	* testsuite/gas/riscv/csr-version-1p9p1.l: Likewise.
	* testsuite/gas/riscv/csr-version-1p10.d: Likewise, but the
	privileged spec is 1.10..
	* testsuite/gas/riscv/csr-version-1p10.l: Likewise.
	* testsuite/gas/riscv/csr-version-1p11.d: Likewise, but the
	privileged spec is 1.11.
	* testsuite/gas/riscv/csr-version-1p11.l: Likewise.
	* testsuite/gas/riscv/csr-version-1p12.d: Likewise, but the
	privileged spec is 1.12.
	* testsuite/gas/riscv/csr-version-1p12.l: Likewise.
	* testsuite/gas/riscv/priv-reg*: Removed or Renamed.