drivers/intel/gma: drop intel_gma_get_controller_info()

Drop function prototype, since all implementations have been removed.

Change-Id: I2e7b5ac7352a1434652b5e6d37bb3744c68b2328
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39962
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/drivers/intel/gma/i915.h

@@ -99,8 +99,6 @@ struct i915_gpu_controller_info
 
 void
 drivers_intel_gma_displays_ssdt_generate(const struct i915_gpu_controller_info *conf);
-const struct i915_gpu_controller_info *
-intel_gma_get_controller_info(void);
 
 /* vbt.c */
 struct device;