m68k: use bcd2bin/bin2bcd

This patch changes m68k to use the new bcd2bin/bin2bcd functions instead
of the obsolete BCD_TO_BIN/BIN_TO_BCD/BCD2BIN/BIN2BCD macros.

It also remove local bcd2bin/bin2bcd implementations
in favor of the global ones.

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>