amdgcn: Fix instruction generation for exp2 and log2 operations

amdgcn: Fix instruction generation for exp2 and log2 operations

The GCN instructions for the exp2 and log2 operations are v_exp_* and v_log_*
respectively, which unfortunately do not line up with the RTL naming
convention.  To deal with this, a new set of int attributes is now used when
generating the assembly for these instructions.

2022-09-27  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* config/gcn/gcn-valu.md (math_unop_insn): New attribute.
	(<math_unop><mode>2, <math_unop><mode>2<exec>, <math_unop><mode>2,
	<math_unop><mode>2<exec>, *<math_unop><mode>2_insn,
	*<math_unop><mode>2<exec>_insn): Use math_unop_insn to generate
	assembler output.