soc/intel/skylake: Define IFD_CHIPSET

This change defines IFD_CHIPSET as sklkbl to allow ifdtool to set the
right access control bits for SKL/KBL platforms.

BUG=b:76098647
BRANCH=poppy
TEST=Verified that the access control bits on KBL platforms are set correctly.

Change-Id: I7b2131caa06d6a975e703262931ec0ea519a86aa
Signed-off-by: Furquan Shaikh <furquan@google.com>
Reviewed-on: https://review.coreboot.org/25307
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/soc/intel/skylake/Kconfig

@@ -355,4 +355,8 @@ config SOC_INTEL_COMMON_LPSS_UART_CLK_N_VAL
 	hex
 	default 0xc35
 
+config IFD_CHIPSET
+	string
+	default "sklkbl"
+
 endif