soc/intel/apollolake: use fast_spi_cache_bios_region()

soc/intel/apollolake: use fast_spi_cache_bios_region()

The fast_spi_cache_bios_region() does the necessary lookup
of BIOS region size, etc. Don't inline the calculation and
just defer to the common piece of code for memory-mapped
spi flash boot.

Change-Id: I6c390aa5a57244308016cd59679d8c3ab02031b8
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/20116
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Barnali Sarkar <barnali.sarkar@intel.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>