RISC-V: Add norelax function attribute

This patch adds norelax function attribute that be discussed in riscv-c-api-doc PR#94.
URL:https://github.com/riscv-non-isa/riscv-c-api-doc/pull/94

gcc/ChangeLog:

	* config/riscv/riscv.cc (riscv_declare_function_name): Add new
	attribute.
2 files changed