ARM: shmobile: Remove sh73a0_get_core_count()

Reduce the number of lines of code in smp-sh73a0.c
by getting rid of the sh73a0_get_core_count() function.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>