rt2x00: remove stray semicolon

The stray semicolon after DEBUG_PRINTK_MSG causes things
like "if (...) WARNING(...); else {}" to fail with syntax error.

Signed-off-by: Johannes Stezenbach <js@sig21.net>
Acked-by: Gertjan van Wingerde <gwingerde@gmail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>