fs/exfat: Make exFAT integrated in kernel by default

Signed-off-by: zwliew <zhaoweiliew@gmail.com>

Conflicts:
	arch/arm/configs/psn_i9300_omni_v2.5d_defconfig
	arch/arm/configs/psn_i9300_v2.5d_defconfig
	arch/arm/configs/psn_i9305_omni_v2.5d_defconfig
	arch/arm/configs/psn_i9305_v2.5d_defconfig

Change-Id: Iff601ccab86a33306d6f74dd7edfcca3aaebf3c3