clk: mmp: Remove old non-OF clock drivers

There are no MMP2, PXA168 or PXA910 boards still using board files which
would use these drivers, so remove them.

Signed-off-by: Duje Mihanović <duje.mihanovic@skole.hr>
Link: https://lore.kernel.org/r/20230804-drop-old-mmp-clk-v1-1-0c07db6cee90@skole.hr


Signed-off-by: Stephen Boyd <sboyd@kernel.org>