[PowerPC] Incorrect and/anyext interchange in custom combine

[nikic]

; RUN: llc -mtriple=powerpc64le-unknown-unknown -ppc-asm-full-reg-names < %s
define void @test(i32 %x, ptr %p) {
  %lshr = lshr i32 %x, 1
  %zext = zext i32 %lshr to i48
  %and = and i48 %zext, 255
  store i48 %and, ptr %p
  ret void
}

Results in:

	rlwinm r3, r3, 31, 24, 31
	stw r3, 0(r4)
	blr

Note the missing store of the upper 16 bits.

This is caused by an incorrect custom DAGCombine added in b0e249d.

[llvmbot]

@llvm/issue-subscribers-backend-powerpc

Author: Nikita Popov (nikic)

```llvm ; RUN: llc -mtriple=powerpc64le-unknown-unknown -ppc-asm-full-reg-names < %s define void @test(i32 %x, ptr %p) { %lshr = lshr i32 %x, 1 %zext = zext i32 %lshr to i48 %and = and i48 %zext, 255 store i48 %and, ptr %p ret void } ``` Results in: ``` rlwinm r3, r3, 31, 24, 31 stw r3, 0(r4) blr ``` Note the missing store of the upper 16 bits.

This is caused by an incorrect custom DAGCombine added in b0e249d.