ppc: Remove MPC8349ITX board

This board relies on using CONFIG_LIBATA but does not enable CONFIG_AHCI.  The
deadline for this conversion was the v2019.07 release.  The use of CONFIG_AHCI
requires CONFIG_DM.  The deadline for this conversion was v2020.01.  Remove
this board.

Signed-off-by: Tom Rini <trini@konsulko.com>