RISC-V: avoid splitting small constant in <or_optab>i<mode>_extrabit pattern

RISC-V: avoid splitting small constant in <or_optab>i<mode>_extrabit pattern

there is no need to split an xori/ori with an small constant. take the test
case `int foo(int idx) { return idx|3; }` as an example,

rv64im_zba generates:
        ori     a0,a0,3
        ret
but, rv64im_zba_zbs generates:
        ori     a0,a0,1
        ori     a0,a0,2
        ret

with this change, insn `ori r2,r1,3` will not be splitted in zbs.

gcc/
	* config/riscv/predicates.md (uimm_extra_bit_or_twobits): Adjust
	predicate to avoid splitting arith constants.

gcc/testsuite

	* gcc.target/riscv/zbs-extra-bit-or-twobits.c: New test.