fix(ti): do not stop non-secure timer on world switch

As stated in the commit introducing the NS_TIMER_SWITCH build flag,
saving/restoring this registers causes the non-secure timer to stop
while in the secure world and non-secure timer interrupts are prevented
from asserting until we return to the non-secure world. This breaks
any realtime OS on the non-secure side that uses this timer for
realtime scheduling.

This flag is by default off, but OP-TEE SPD enables it. The K3 OP-TEE
platform makes no use of these registers and we would like to have
support for realtime OSs while also supporting the OP-TEE SPD. Disable
this flag in our platform definition.

Signed-off-by: Andrew Davis <afd@ti.com>
Change-Id: I65055512d897b93b7690fd63c734f4731a6e09e6

plat/ti/k3/common/plat_common.mk

@@ -28,6 +28,8 @@ ERRATA_A72_1319367	:=	1
 
 CRASH_REPORTING		:= 1
 
+NS_TIMER_SWITCH		:=	0
+
 # Split out RO data into a non-executable section
 SEPARATE_CODE_AND_RODATA :=    1