Speedup BGX link polling on ARM64

The previous values caused the callout thread stall for 100ms each 2s
if no link is present. Dtrace analysis showed that it has significant
impact on overall interrupt performance.
Decrease these values by a factor of 100.

Obtained from: Semihalf
Sponsored by: Cavium
Reviewed by: zbb
Differential Revision: https://reviews.freebsd.org/D5854