diag: Initialize local variables

Fix the issue seen below, when flags_sec is uninitialized.

drivers/char/diag/diag_memorydevice.c: In function 'diag_md_write':
./include/linux/spinlock.h:261:3: warning: 'flags_sec' may be used
uninitialized in this function [-Wmaybe-uninitialized].

This patch initializes the local variable flags_sec.

Change-Id: I28a05d8c54468bb7f75f90dea69e074e27ff4a26
Signed-off-by: Anant Goel <anantg@codeaurora.org>