fix(arm): resolve misra rule R11.6 violation

Fixed below MISRA violation:
- MISRA violation: MC3R1.R11.6:
  - A cast shall not be performed between a pointer to void and an
    arithmetic data type. (i.e cast from integer to void*)
- Fix:
  - cast via portable and misra compliant type "uintptr_t" and
    use 0U instead of NULL for comparisons.

Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>
Change-Id: Ie3a7561d9a254027c5364485a1d72fc1320dfcad
1 file changed