RISC-V: Fix minor issues with FP csr instructions.

RISC-V: Fix minor issues with FP csr instructions.

	Mel Chen <mel.chen@sifive.com>
	gas/
	* testsuite/gas/riscv/alias-csr.s: Add testcase for CSR-access
	alias instructions.
	* testsuite/gas/riscv/no-aliases-csr.d: Run testcase alias-csr.s with
	-Mno-aliases.
	* testsuite/gas/riscv/alias-csr.d: Run testcase alias-csr.s.
	* testsuite/gas/riscv/priv-reg.d: Update.
	opcodes/
	* riscv-opc.c (riscv_opcodes): Set frsr, fssr, frcsr, fscsr, frrm,
	fsrm, fsrmi, frflags, fsflags, fsflagsi to alias instructions.
	* riscv-opc.c (riscv_opcodes): Adjust order of frsr, frcsr, fssr,
	fscsr.