RISC-V: Enforce Libatomic LR/SC SEQ_CST

Replace LR.aq/SC.rl pairs with the SEQ_CST LR.aqrl/SC.rl pairs
recommended by table A.6 of the ISA manual.

2023-04-27 Patrick O'Neill <patrick@rivosinc.com>

libgcc/ChangeLog:

	* config/riscv/atomic.c: Change LR.aq/SC.rl pairs into
	sequentially consistent LR.aqrl/SC.rl pairs.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>