Use a common tsec_mii_wait() function to busy wait for status changes.

The status indicators are not set immediatly after a command. Discard
the first value.

Unlock the PHY mutex after a timeout in tsec_init_locked().

Tested on the P1020RDB.

Submitted by: Sebastian Huber <sebastian_DOT_huber_AT_embedded-brains_DOT_de>