ARM: shmobile: r8a7779: Move r8a7779_earlytimer_init to clock-r8a7779.c

r8a7779_earlytimer_init() calls r8a7779_clock_init() and
r8a7779_clock_init() is defined in clock-r8a7779.c.

If both CONFIG_COMMON_CLK and CONFIG_ARCH_R8A7779 are enabled,
as will be the case when marzen-reference moves to use
the common clock framework, then setup-r8a7779.c is compiled
but clock-r8a7779.c is not.

As r8a7779_earlytimer_init() is not used by marzen-reference
simply move it to clock-r8a7779.c.

[horms+renesas@verge.net.au: rebase]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>