Import ctzdi2.c from LLVM compiler-rt ...

When using __builtin_ctzll() in AArch32 code, the compiler may translate
that into a call to the __ctzdi2() function. In this case, the linking
phase fails because TF doesn't provide an implementation for it.

This patch imports the implementation of the __ctzdi2() function from
LLVM's compiler-rt project and hooks it into TF's build system. The
ctzdi2.c file is an unmodified copy from the master branch as of
July 19 2017 (SVN revision: 308480).

Change-Id: I96766a025ba28e1afc6ef6a5c4ef91d85fc8f32b
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>

compiler-rt: Remove unused int_util.[ch] files ...

Change-Id: I32fc523e3178b7e50191682241904d52499ff708
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

Hook up LLVM compiler-rt in the build system ...

This patch enables compiler-rt for the AArch32 target.  The code is
not used for AArch64 as the architecture supports the 64-bit division
and modulo operations natively.

Change-Id: I1703a92872b0bb56ac0b98c67193830683963b13
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>

Import builtins from LLVM compiler-rt project ...

These are needed to provide division and modulo operations
for the AArch32 target.

This code is entirely unmodified.  Imported from compiler-rt
master branch as of May 4 2017.

Change-Id: I001e1809f2afd4bf8d4cc3d2296798809f607144
Signed-off-by: dp-arm <dimitris.papastamos@arm.com>