RISC-V: Adjusting the comments of the emit_vlmax_insn/emit_vlmax_insn_lra/emit_nonvlm...

RISC-V: Adjusting the comments of the emit_vlmax_insn/emit_vlmax_insn_lra/emit_nonvlmax_insn functions

V2 Change: Use Robin's comments.

This patch adjusts the comments of the
emit_vlmax_insn/emit_vlmax_insn_lra/emit_nonvlmax_insn functions.
The purpose of the adjustment is to make it clear that vlmax here is not
VLMAX as defined inside the RVV ISA. This is because this function is used
by RVV mode (e.g. RVVM1SImode) in addition to VLS mode (V16QI). For RVV mode,
it means the same thing, for VLS mode, it indicates setting the vl to the
number of units of the mode. Changed the comment because I didn't think of
a better name. If there is a suitable name, feel free to discuss it.

gcc/ChangeLog:

	* config/riscv/riscv-v.cc (emit_vlmax_insn): Adjust comments.
	(emit_nonvlmax_insn): Adjust comments.
	(emit_vlmax_insn_lra): Adjust comments.

Co-Authored-By: Robin Dapp <rdapp.gcc@gmail.com>