soc/amd/picasso/fch: make sb_clk_output_48Mhz static

sb_clk_output_48Mhz is only used in fch.c where it is also implemented,
so no need to have it visible outside of that compilation unit.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I2b0d10ff26bdf54ea791aa66bf400578466d54cf
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56525
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/amd/picasso/fch.c

@@ -86,7 +86,7 @@ const struct irq_idx_name *sb_get_apic_reg_association(size_t *size)
 	return irq_association;
 }
 
-void sb_clk_output_48Mhz(void)
+static void sb_clk_output_48Mhz(void)
 {
 	u32 ctrl;
 	const struct soc_amd_picasso_config *cfg = config_of_soc();

src/soc/amd/picasso/include/soc/southbridge.h

@@ -151,7 +151,6 @@ void fch_final(void *chip_info);
 
 void enable_aoac_devices(void);
 void wait_for_aoac_enabled(unsigned int dev);
-void sb_clk_output_48Mhz(void);
 
 /* Allow the board to change the default I2C pad configuration */
 void mainboard_i2c_override(int bus, uint32_t *pad_settings);