intel/apollolake: Add car.c to verstage

Verstage on apollolake requires the functions defined in car.c to
perform flush of l1d to l2 on loading romstage into CAR.

Change-Id: I6d9a0b9dfb58c2126ad70172846e90663e588857
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/15046
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/apollolake/Makefile.inc

@@ -59,6 +59,7 @@ postcar-y += mmap_boot.c
 postcar-$(CONFIG_SOC_UART_DEBUG) += uart_early.c
 postcar-y += tsc_freq.c
 
+verstage-y += car.c
 verstage-y += memmap.c
 verstage-y += mmap_boot.c
 verstage-$(CONFIG_SOC_UART_DEBUG) += uart_early.c