soc: tegra-pmc: add API to show last reset status

soc: tegra-pmc: add API to show last reset status

Export API to show last reset reason, so that if other
driver need to act on particular reset source, they can act
based reset status.
For example, if other driver need to do some work
if watchdog-timeout was the last reset-reason, that driver can call
this API to get the last reset status and based on reset-status,
driver can proceed further.

Bug 1846039

Change-Id: I980985770bbe2307ea0d85976eca74aae28f155d
Signed-off-by: Jeetesh Burman <jburman@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/1544981
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bibek Basu <bbasu@nvidia.com>