[tuna] GPS: Fix security hole

Change a permssion for /proc/mcspi1_cs3_ctrl as 600.
With this patch, there is no GPS operation issue.
Bug ID : 7494980

Change-Id: I4446c2805a0d47a803f9f3ca1f5bce26371653d3
Signed-off-by: Sangcheol Lee <goodsc.lee@samsung.com>