mailbox: check for bit set before polling
mailbox: check for bit set before polling

Before polling we just need to see if the TXDONE_BY_POLL bit
is set in txdone_method. There may be another bit (method)
specified as well, like TXDONE_BY_ACK.

Signed-off-by: Jassi Brar <0830630c6cd5183ace1d4c7d6bf00ba9c2282b5f@gmail.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs