soc: brcmstb: fix warning from missing include

The brcmstb_biuctrl_init() is defined in the soc specific header
file, but wasn't included in the driver file. Fix the following
warning by including <linux/soc/brcmstb/brcmstb.h> in the driver:

drivers/soc/brcmstb/biuctrl.c:101:13: warning: symbol 'brcmstb_biuctrl_init' was not declared. Should it be static?
Signed-off-by: NBen Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>

drivers/soc/bcm/brcmstb/biuctrl.c

@@ -19,6 +19,7 @@
 #include <linux/io.h>
 #include <linux/of_address.h>
 #include <linux/syscore_ops.h>
+#include <linux/soc/brcmstb/brcmstb.h>
 
 #define CPU_CREDIT_REG_OFFSET			0x184
 #define  CPU_CREDIT_REG_MCPx_WR_PAIRING_EN_MASK	0x70000000