intel/apollolake/spi: Add support for reading status reg

spi_read_status reads the status register using hardware sequencing and
returns 0 on success and -1 on error. Use spi_read_status to return
appropriate value for get_sw_write_protect.

BUG=chrome-os-partner:54283

Change-Id: I7650b5c0ab05a8429c2b291f00d4672446d86e03
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/15266
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/Makefile.inc

@@ -30,6 +30,7 @@ romstage-y += mmap_boot.c
 romstage-y += tsc_freq.c
 romstage-y += pmutil.c
 romstage-y += reset.c
+romstage-y += spi.c
 
 smm-y += mmap_boot.c
 smm-y += pmutil.c