[to-be-committed,RISC-V] Improve AND with some constants

[to-be-committed,RISC-V] Improve AND with some constants

If we have an AND with a constant operand and the constant operand
requires synthesis, then we may be able to generate more efficient code
than we do now.

Essentially the need for constant synthesis gives us a budget for
alternative ways to clear bits, which zext.w can do for bits 32..63
trivially.   So if we clear 32..63  via zext.w, the constant for the
remaining bits to clear may be simple enough to use with andi or bseti.
That will save us an instruction.

This has tested in Ventana's CI system as well as my own.  I'll wait for
the upstream CI tester to report success before committing.

Jeff
gcc/
	* config/riscv/bitmanip.md: Add new splitter for AND with
	a constant that masks off bits 32..63 and needs synthesis.

gcc/testsuite/

	* gcc.target/riscv/zba_zbs_and-1.c: New test.