gpu: arm: mali400: add workaround code for secure access

gpu: arm: mali400: add workaround code for secure access

This modification brought from r6p2_01rel0.

This patch adds workaround code for s5p4418. If s5p4418 runs kernel in
normal mode, access to mali register induces fault like below message.
"Unhandled fault: imprecise external abort (0x406) at 0xbe8bcdd0"
Access to mali register is possible by psci secure access extension.
This patch uses {write|read}_sec_reg api that is made for this case.

Change-Id: I23cc60047f81dafb6e8c22e568bccba30373522e
Signed-off-by: jino.cho <jino.cho@samsung.com>