[RSIC-V] Fix 32bit riscv with zbs extension enabled

The problem here was a disconnect between splittable_const_int_operand
predicate and the function riscv_build_integer_1 for 32bits with zbs enabled.
The splittable_const_int_operand predicate had a check for TARGET_64BIT which
was not needed so this patch removed it.

Committed as obvious after a build for risc32-elf configured with --with-arch=rv32imac_zba_zbb_zbc_zbs.

Thanks,
Andrew Pinski

gcc/ChangeLog:

	* config/riscv/predicates.md (splittable_const_int_operand):
	Remove the check for TARGET_64BIT for single bit const values.