The libSYS/include/machine_type.h header file states LONG should be
"Data type representing 4 byte signed integer on all supported
platforms" but only provided for defining LONG as INT and ULONG as
UINT when __x86_64__ was defined. This has been changed to when
__LP64__ is defined, so that it also applies to AArch64. The change
to libFDK/include/common_fix.h is then needed to get the project to
compile.

Change-Id: Iea42d7eca97dcc9da772a05b207d134cb999a72a
Signed-off-by: Marcus Oakland <marcus.oakland@arm.com>