mpc83xx: remove 3.7 support

target/linux/mpc83xx/config-3.7

.../mpc83xx/patches-3.7/100-powerpc_create_fit_uImages.patch

...83xx/patches-3.7/101-mpc8377_wlan-dts-add-gpio-leds.patch

target/linux/mpc83xx/patches-3.7/110-vitesse_8601.patch

target/linux/mpc83xx/patches-3.7/111-etsec27_war.patch

target/linux/mpc83xx/patches-3.7/120-ucc_tdm.patch

...x/mpc83xx/patches-3.7/200-powerpc-add-rbppc-support.patch

.../linux/mpc83xx/patches-3.7/201-powerpc-add-rb_iomap.patch

...pc83xx/patches-3.7/202-ata-add-pata_rbppc_cf-driver.patch

...x/mpc83xx/patches-3.7/203-mtd-add-rbppc_nand-driver.patch

.../patches-3.7/300-mpc8377_wlan-dts-add-openwrt-hacks.patch