ssb: remove invalid define SSB_TMSLOW_PHYCLK

It was incorrectly introduced in d2730b2a

. We
have already fixed function to use correct define, but forgot remove old one.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: Gábor Stefanik <netrolller.3d@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>