feat(fvp): add plat API to set and get the DRTM error

Added a platform function to set and get DRTM error.
Also, added a platform function to reset the system.

Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
Change-Id: I471f2387f8c78b21a06af063a6fa02cda3646557
diff --git a/include/plat/arm/common/plat_arm.h b/include/plat/arm/common/plat_arm.h
index d060332..6c0d91d 100644
--- a/include/plat/arm/common/plat_arm.h
+++ b/include/plat/arm/common/plat_arm.h
@@ -297,6 +297,7 @@
 void plat_arm_program_trusted_mailbox(uintptr_t address);
 bool plat_arm_bl1_fwu_needed(void);
 __dead2 void plat_arm_error_handler(int err);
+__dead2 void plat_arm_system_reset(void);
 
 /*
  * Optional functions in ARM standard platforms