stmmac: Fix incorrect spinlock release and PTP cap detection.

This patch corrects a problem in stmmac_ptp.c, functions
stmmac_adjust_time and stmmac_adjust_freq where the incorrect spinlocks
were released. This patch also addresses a problem in stmmac_main,
function stmmac_init_ptp where the capability detection for
advanced timestamping was masked by message masking.

This patch was touch tested using linuxptp, and runs without the previously
observed instabilities. More extensive testing is ongoing.

Vince

Signed-off-by: Vince Bridgers <vbridgers2013@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>