defconfig: arm: msm: Enable FW_LOADER_USER_HELPER_FALLBACK config flag

This enables udev firmware loading, though kernel fails direct
file loading. This is must need config for loading GPU firmware.
msm8937_defconfig is used for msm8937 target and
msmcortex_defconfig is used for msmtitanium SoC.

Change-Id: I0b85846d2748bc1ff6700c5170b4832afa1f3a32
Signed-off-by: Hareesh Gundu <hareeshg@codeaurora.org>