Remove sa1100.h

sa1100.h is not used anywhere, then remove it.

$ find . -name '*.h' -empty -print
./include/sa1100.h
$ git grep 'sa1100.h' .
$

Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi@necel.com>
Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>