aarch32: Allow compiling with soft-float toolchain

aarch32: Allow compiling with soft-float toolchain

ARMv7 and Cortex-A32(ARMv8/aarch32) uses "arm-linux-gnueabi" toolchain which
has both soft-float and hard-float variants and so there could be scenarios
where soft-float toolchain is used.Even though TF-A documentation recommends
to use hard-float toolchain for aarch32 but there are external projects where
we cannot mandate the selection of toolchain and for those projects at least
the build should not fail.

Current TF-A source fails to build with soft-float toolchain because assembler
does not recognizes "vmsr" instruction which is required to enable floating
point unit.

To avoid this piece of code being compiled with soft-float toolchain add
predefined macro guard " __SOFTFP__" exposed by soft-float toolchain.

Change-Id: I76ba40906a8d622dcd476dd36ab4d277a925996c
Signed-off-by: Manish Pandey <[email protected]>