arm: Don't test x264_cpu_fast_neon_mrc_test on Windows

The performance counters themselves are accessible, but the PMNC (control register) that we try to read to see if the performance counters are accessible, is not readable, causing illegal instructions in cpu_enable_armv7_counter.

As an alternative, we could also modify cpu_fast_neon_mrc_test to not inspect the PMNC at all (skip calling cpu_enable_armv7_counter) but just assume that the counters are available, in high resolution mode. However just not calling this codepath is the simplest, as Windows on 32 bit ARM isn't very relevant these days.