Convert CONFIG_SPL_FAT_SUPPORT to Kconfig

configs/draco_defconfig

configs/etamin_defconfig

configs/novena_defconfig

configs/pcm051_rev1_defconfig

configs/pcm051_rev3_defconfig

configs/pengwyn_defconfig

configs/pepper_defconfig

configs/picosam9g45_defconfig

configs/pxm2_defconfig

configs/rastaban_defconfig

configs/rut_defconfig

configs/sama5d2_xplained_mmc_defconfig

configs/sama5d3_xplained_mmc_defconfig

configs/sama5d3xek_mmc_defconfig

configs/sama5d4_xplained_mmc_defconfig

configs/sama5d4ek_mmc_defconfig

configs/thuban_defconfig

configs/ti814x_evm_defconfig

configs/ti816x_evm_defconfig

configs/xilinx_zynqmp_zc1751_xm016_dc2_defconfig