ArmPkg/ArmSoftFloatLib: add support for RVCT

ArmPkg/ArmSoftFloatLib: add support for RVCT

The ARM softfloat library in ArmSoftfloatLib currently does not build
under RVCT, simply because the code includes system header files that
RVCT does not provide. However, nothing exported by those include files
is actually used by the library when built in SOFTFLOAT_FOR_GCC mode,
so we can just drop all of them.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@19031 6f19259b-4bc3-4df7-8a09-765794883524