ARM: Fix the world famous typo with is_gate_vma()

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/kernel/process.c

@@ -459,7 +459,7 @@ int in_gate_area_no_mm(unsigned long addr)
 {
 	return in_gate_area(NULL, addr);
 }
-#define is_gate_vma(vma)	((vma) = &gate_vma)
+#define is_gate_vma(vma)	((vma) == &gate_vma)
 #else
 #define is_gate_vma(vma)	0
 #endif