nb/intel/gm45: Make fetching the blc_pwm freq global

This can be used to select the proper VBT.

Change-Id: Id3f6ba3ae31a5ab47f44d207678c1c4a6a43b7ec
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/29925
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>

src/northbridge/intel/gm45/gm45.h

@@ -442,6 +442,7 @@ struct blc_pwm_t {
 	int pwm_freq; /* In Hz */
 };
 int get_blc_values(const struct blc_pwm_t **entries);
+u16 get_blc_pwm_freq_value(const char *edid_ascii_string);
 
 
 #if ENV_RAMSTAGE && !defined(__SIMPLE_DEVICE__)

src/northbridge/intel/gm45/gma.c

@@ -668,7 +668,7 @@ static u32 freq_to_blc_pwm_ctl(struct device *const dev,
 		return (blc_mod << 16) | blc_mod;
 }
 
-static u16 get_blc_pwm_freq_value(const char *edid_ascii_string)
+u16 get_blc_pwm_freq_value(const char *edid_ascii_string)
 {
 	static u16 blc_pwm_freq;
 	const struct blc_pwm_t *blc_pwm;