RISC-V: Fix implicit dependency of Zabha and Zacas

1 Zabha depends on Zaamo:
<https://github.com/riscv/riscv-isa-manual/blob/main/src/zabha.adoc>

2 Zacas depends on Zaamo:
<https://github.com/riscv/riscv-isa-manual/blob/main/src/zacas.adoc>

bfd/ChangeLog:

	* elfxx-riscv.c: Zabha and Zacas implicitly depend on Zaamo.

gas/ChangeLog:

	* testsuite/gas/riscv/imply.d: Updated.

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