ARM: shmobile: Remove unused shmobile_smp_init_fallback_ops()

shmobile_smp_init_fallback_ops() became unused after removing
SoC-specific machine definitions that provided legacy SMP initialization
fallbacks.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>