cppcheck detected a condition which was always false.

According to the MCIMX31 Reference Manual, the PRCS bits have to be 01
to select the Frequency Pre-Multiplier (FPM). PRCS uses bits 1 and 2,
so we have to test for 2.
Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NPeter Chubb <peter.chubb@nicta.com.au>
Message-id: 1370810662-32320-1-git-send-email-sw@weilnetz.de
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>