Use bitwise clear instead of `not` + `and` for _mm_testc_si128
Use bitwise clear instead of `not` + `and` for _mm_testc_si128

Not all compilers seem to perform this optimisation, so explicitly call
the bitwise clear intrinsic.

Example codegen for _mm_testc_si128(a, b) with GCC 11.2.0 (-O3):

Prior to commit:
    mvn     v0.16b, v0.16b
    and     v1.16b, v1.16b, v0.16b
    fmov    d0, d1
    mov     d1, v1.d[1]
    orr     v0.8b, v0.8b, v1.8b
    fmov    x0, d0
    cmp     x0, 0x0
    cset    w0, eq  // eq = none

After commit:
    bic     v0.16b, v1.16b, v0.16b
    fmov    d1, d0
    mov     d0, v0.d[1]
    orr     v0.8b, v1.8b, v0.8b
    fmov    x0, d0
    cmp     x0, 0x0
    cset    w0, eq  // eq = none

DLTcollab/sse2neon,DLTcollab/sse2neon,DLTcollab/sse2neon