gma: Introduce `PCH_Type`

We got this far without it but now there is a PCH (Cannon Point)
that is not fully compatible to its predecessors but works with
the same CPUs. First, introduce the type and make use of it in a
few cases. In a follow-up, we'll add the new PCH.

Change-Id: I9d4965f110da3613749023143cf75123e63ae76e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/libgfxinit/+/48762
Reviewed-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
diff --git a/common/Makefile.inc b/common/Makefile.inc
index f2a2fbb..b1ed074 100644
--- a/common/Makefile.inc
+++ b/common/Makefile.inc
@@ -47,11 +47,13 @@
 gfxinit-y += hw-gfx-framebuffer_filler.adb
 gfxinit-y += hw-gfx-framebuffer_filler.ads
 
+CONFIG_GFX_GMA_PCH		?= No_PCH
 CONFIG_GFX_GMA_PANEL_2_PORT	?= Disabled
 
 CONFIG_GFX_GMA_GENERATION	:= $(call strip_quotes,$(CONFIG_GFX_GMA_GENERATION))
 CONFIG_GFX_GMA_CPU		:= $(call strip_quotes,$(CONFIG_GFX_GMA_CPU))
 CONFIG_GFX_GMA_CPU_VARIANT	:= $(call strip_quotes,$(CONFIG_GFX_GMA_CPU_VARIANT))
+CONFIG_GFX_GMA_PCH		:= $(call strip_quotes,$(CONFIG_GFX_GMA_PCH))
 CONFIG_GFX_GMA_PANEL_1_PORT	:= $(call strip_quotes,$(CONFIG_GFX_GMA_PANEL_1_PORT))
 CONFIG_GFX_GMA_PANEL_2_PORT	:= $(call strip_quotes,$(CONFIG_GFX_GMA_PANEL_2_PORT))
 CONFIG_GFX_GMA_ANALOG_I2C_PORT	:= $(call strip_quotes,$(CONFIG_GFX_GMA_ANALOG_I2C_PORT))
@@ -76,6 +78,7 @@
 
 GFX_GMA_COMMON_SUBSTITUTIONS := \
 	    -e's/<<GEN>>/$(CONFIG_GFX_GMA_GENERATION)/' \
+	    -e's/<<PCH>>/$(CONFIG_GFX_GMA_PCH)/' \
 	    -e's/<<PANEL_1_PORT>>/$(CONFIG_GFX_GMA_PANEL_1_PORT)/' \
 	    -e's/<<PANEL_2_PORT>>/$(CONFIG_GFX_GMA_PANEL_2_PORT)/' \
 	    -e's/<<ANALOG_I2C_PORT>>/$(CONFIG_GFX_GMA_ANALOG_I2C_PORT)/' \