arm: defconfig: set gememalloc as built-in
Seems necessary to avoid an intermittant hang during boot.
Stock kernel also seems to do this, despite it being specified
as a module via the source defconfig.

Commit: https://github.com/androidarmv6/android_kernel_samsung_bcm21553-common/commit/d61a2f5b5630a714354b319691f20a36ee0d181e