mali_kbase: fix implicit fall-through errors

Fixes several -Wimplicit-fallthrough errors similar to:

  gpu/mali_kbase/mali_kbase_pm.c:80:3:
  error: unannotated fall-through between switch labels [-Werror,-Wimplicit-fallthrough]
                case KBASE_PM_SUSPEND_HANDLER_DONT_INCREASE:
                ^
  gpu/mali_kbase/mali_kbase_pm.c:80:3:
  note: insert '__attribute__((fallthrough));' to silence this warning
                case KBASE_PM_SUSPEND_HANDLER_DONT_INCREASE:
                ^
                __attribute__((fallthrough));
  gpu/mali_kbase/mali_kbase_pm.c:80:3:
  note: insert 'break;' to avoid fall-through
                case KBASE_PM_SUSPEND_HANDLER_DONT_INCREASE:
                ^
                break;

Bug: 215617713
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Change-Id: I3a02e020583ce47d0812433cc939c1b066ae7e3a