drivers/intel/gma: Move gfxinit into sub package

Move the actual graphics init provided by libgfxinit into a sub package
`GMA.GFX_Init`. This way it can be compiled in individually.

Change-Id: Ib413a0d70c8dc305f4476c1d5aee6b81ff880bec
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/31456
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/drivers/intel/gma/gma-gfx_init.ads

@@ -0,0 +1,38 @@
+with Interfaces.C;
+
+with HW;
+use HW;
+
+package GMA.GFX_Init
+is
+
+   procedure gfxinit (lightup_ok : out Interfaces.C.int);
+   pragma Export (C, gfxinit, "gma_gfxinit");
+
+   ----------------------------------------------------------------------------
+
+   type lb_framebuffer is record
+      tag                  : word32;
+      size                 : word32;
+
+      physical_address     : word64;
+      x_resolution         : word32;
+      y_resolution         : word32;
+      bytes_per_line       : word32;
+      bits_per_pixel       : word8;
+      red_mask_pos         : word8;
+      red_mask_size        : word8;
+      green_mask_pos       : word8;
+      green_mask_size      : word8;
+      blue_mask_pos        : word8;
+      blue_mask_size       : word8;
+      reserved_mask_pos    : word8;
+      reserved_mask_size   : word8;
+   end record;
+
+   function fill_lb_framebuffer
+     (framebuffer : in out lb_framebuffer)
+      return Interfaces.C.int;
+   pragma Export (C, fill_lb_framebuffer, "fill_lb_framebuffer");
+
+end GMA.GFX_Init;