ARM: shmobile: Remove SH7377 support

This is old CPU of shmobile, and the machine by which this CPU is
used cannot be obtained.
Therefore, remove SH7377 support.

Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.yj@renesas.com>
Signed-off-by: Simon Horman <horms@verge.net.au>