common/memtest.c: Refactor mem_test() into three surbroutines
Original mem_test() was rather long an contained code to perform two
distinct operations. This patch moves that code into two separate
subroutines and converts mem_test into a high level interface that
calls the subroutines.
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>