ARM: shmobile: genmai-reference: Remove legacy clock support

genmai-reference is now only built for multiplatform which means that
CCF comes with the package. Remove unused legacy code ifdefs to clean up
the code.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>