mediatek: mt7622: no longer select FIT_PARTITION

mediatek: mt7622: no longer select FIT_PARTITION

All mt7622 board previously using the FIT partition parser have been
converted to use the fitblk driver:
 6aec3c7b5b mediatek: mt7622: modernize Linksys E8450 / Belkin RT3200 UBI build
 41c053141e mediatek: mt7622: convert unifi6lr-v{1,2,3}-ubootmod to fitblk
 208f6c1232 mediatek: mt7622: convert BPi-R64 to all-UBI layout and fitblk

Remove the now no longer needed FIT partition parser from builds for
mt7622.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>