sh: Tidy up NEFF-based sign extension for SH-5.

This consolidates all of the NEFF-based sign extension for SH-5.
In the future the other SH code will need to make use of this as well,
so make it generic in preparation for more 32/64 consolidation.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/include/asm/pgtable.h b/arch/sh/include/asm/pgtable.h
index 43ef3e9..3cd7127 100644
--- a/arch/sh/include/asm/pgtable.h
+++ b/arch/sh/include/asm/pgtable.h
@@ -36,6 +36,12 @@
 #define	NEFF_SIGN	(1LL << (NEFF - 1))
 #define	NEFF_MASK	(-1LL << NEFF)
 
+static inline unsigned long long neff_sign_extend(unsigned long val)
+{
+	unsigned long long extended = val;
+	return (extended & NEFF_SIGN) ? (extended | NEFF_MASK) : extended;
+}
+
 #ifdef CONFIG_29BIT
 #define NPHYS		29
 #else