firmware: bcm47xx_sprom: Fix -Wmissing-prototypes warnings

bcm47xx_sprom.h did not include a prototype for bcm47xx_fill_sprom()
therefore add one, and make sure we do include that header to fix
-Wmissing-prototypes warnings.

Reported-by: kernel test robot <[e-mail]>
Signed-off-by: Florian Fainelli <[e-mail]>
Signed-off-by: Thomas Bogendoerfer <[e-mail]>

drivers/firmware/broadcom/bcm47xx_sprom.c

···
  */
 
 #include <linux/bcm47xx_nvram.h>
+#include <linux/bcm47xx_sprom.h>
 #include <linux/bcma/bcma.h>
 #include <linux/etherdevice.h>
 #include <linux/if_ether.h>

include/linux/bcm47xx_sprom.h

···
 #include <linux/kernel.h>
 #include <linux/vmalloc.h>
 
+struct ssb_sprom;
+
 #ifdef CONFIG_BCM47XX_SPROM
+void bcm47xx_fill_sprom(struct ssb_sprom *sprom, const char *prefix,
+			bool fallback);
 int bcm47xx_sprom_register_fallbacks(void);
 #else
+static inline void bcm47xx_fill_sprom(struct ssb_sprom *sprom,
+				      const char *prefix,
+				      bool fallback)
+{
+}
+
 static inline int bcm47xx_sprom_register_fallbacks(void)
 {
 	return -ENOTSUPP;