rtlwifi: rtl8192se: Fix firmware loading

An error in the code makes the allocated space for firmware to be too
small.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Murilo Opsfelder Araujo <mopsfelder@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>