Tegra: pmc: fix defects flagged during MISRA analysis

Main fixes:

* Fixed if/while statement conditional to be essentially boolean [Rule 14.4]

* Added curly braces ({}) around if/for/while statements in order to
  make them compound [Rule 15.6]

* Added explicit casts (e.g. 0U) to integers in order for them to be
  compatible with whatever operation they're used in [Rule 10.1]

Change-Id: Ic72b248aeede6cf18bf85051188ea7b8fd8ae829
Signed-off-by: Anthony Zhou <anzhou@nvidia.com>