build: Use hard-float abi

* Specifying ‘soft’ causes GCC to generate output containing
  library calls for floating-point operations.
* ‘softfp’ allows the generation of code using hardware
  floating-point instructions, but still uses the soft-float
  calling conventions.
* ‘hard’ allows generation of floating-point instructions and
  uses FPU-specific calling conventions.

Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>