mcu: apollo: fix compilation issue for bitmask declaration

There are register bitmask in apollox.h that uses -2147483648 to
represent mask value 0x80000000, which would cause compilation
issue with ISO C90. A test case that will face this compilation
issue is tests/lib/cpp/cxx. To fix this issue, the definition
is changed to its hex representation accordingly.

Signed-off-by: Chew Zeh Yang <[email protected]>

Author: zeonchew