pit: Don't configure PB3 in alternate function mode
pit: Don't configure PB3 in alternate function mode

The power button LED is on PA2, not PB3.  Remove a line of code
accidentally left in from copy-paste at the start of pit bringup.

BUG=chrome-os-partner:21676
BRANCH=pit
TEST=boot pit

Change-Id: Id991b16d69bca0a411efa72211c5dc407923240d
Signed-off-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/64714
Reviewed-by: Vic Yang <5fd92abeee651458f98e2856f4f200ee971cee4d@chromium.org>

mtk09422/chromiumos-platform-ec,fourier49/BIZ_EC,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,thehobn/ec,longsleep/ec,thehobn/ec,longsleep/ec,alterapraxisptyltd/chromium-ec,alterapraxisptyltd/chromium-ec,md5555/ec,alterapraxisptyltd/chromium-ec,longsleep/ec,longsleep/ec,coreboot/chrome-ec,coreboot/chrome-ec,fourier49/BZ_DEV_EC,gelraen/cros-ec,alterapraxisptyltd/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,mtk09422/chromiumos-platform-ec,md5555/ec,thehobn/ec,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,gelraen/cros-ec,eatbyte/chromium-ec,coreboot/chrome-ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BIZ_EC,eatbyte/chromium-ec,coreboot/chrome-ec,eatbyte/chromium-ec,gelraen/cros-ec,coreboot/chrome-ec,gelraen/cros-ec,md5555/ec,fourier49/BIZ_EC,fourier49/BZ_DEV_EC,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,thehobn/ec