m68k: Drop CONFIG_MCFPIT support

All platforms currently use the "MCFTMR" DMA timer rather than the PIT
timer, so drop the MCFPIT code.

Cc: Huan Wang <alison.wang@nxp.com>
Cc: Angelo Dureghello <angelo@sysam.it>
Cc: TsiChung Liew <Tsi-Chung.Liew@nxp.com>
Cc: Wolfgang Wegner <w.wegner@astro-kom.de>
Signed-off-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Angelo Dureghello <angelo@sysam.it>