brcm63xx: fix build failure on varid

varid might both unused and unitialized when building for e.g: bcm6318,
fix these two warnings turned into errors.

Signed-off-by: Florian Fainelli <florian@openwrt.org>

SVN-Revision: 39277

target/linux/brcm63xx/patches-3.10/332-MIPS-BCM63XX-detect-bcm6328-variants.patch

@@ -14,7 +14,7 @@ Subject: [PATCH 42/53] MIPS: BCM63XX: detect bcm6328 variants
  	struct cpuinfo_mips *c = &current_cpu_data;
  	unsigned int cpu = smp_processor_id();
  	u32 chipid_reg;
-+	u8 varid;
++	u8 __maybe_unused varid = 0;
  
  	/* soc registers location depends on cpu type */
  	chipid_reg = 0;

target/linux/brcm63xx/patches-3.10/339-MIPS-BCM63XX-add-support-for-BCM63268.patch

@@ -189,7 +189,7 @@ Signed-off-by: Jonas Gorski <jogo@openwrt.org>
  	unsigned int cpu = smp_processor_id();
  	u32 chipid_reg;
 +	bool long_chipid = false;
- 	u8 varid;
+ 	u8 __maybe_unused varid = 0;
  
  	/* soc registers location depends on cpu type */
 @@ -325,6 +356,9 @@ void __init bcm63xx_cpu_init(void)