RISC-V: Add an implicit dependency for Zawrs

RISC-V: Add an implicit dependency for Zawrs

There is a description in <https://github.com/riscv/riscv-isa-manual/blob/main/src/zawrs.adoc>:

"The instructions in the Zawrs extension are only useful in conjunction
with the LR instruction, which is provided by the Zalrsc component
of the A extension."

It can be concluded that: zawrs -> zalrsc.

gcc/ChangeLog:

	* common/config/riscv/riscv-common.cc: zawrs -> zalrsc.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/predef-38.c: New test.
	* gcc.target/riscv/predef-39.c: New test.

Signed-off-by: Xiao Zeng <zengxiao@eswincomputing.com>