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/mm/fault_64.c b/arch/sh/mm/fault_64.c
index bd63b96..2b356ce 100644
--- a/arch/sh/mm/fault_64.c
+++ b/arch/sh/mm/fault_64.c
@@ -56,16 +56,7 @@
 	/*
 	 * Set PTEH register
 	 */
-	pteh = address & MMU_VPN_MASK;
-
-	/* Sign extend based on neff. */
-#if (NEFF == 32)
-	/* Faster sign extension */
-	pteh = (unsigned long long)(signed long long)(signed long)pteh;
-#else
-	/* General case */
-	pteh = (pteh & NEFF_SIGN) ? (pteh | NEFF_MASK) : pteh;
-#endif
+	pteh = neff_sign_extend(address & MMU_VPN_MASK);
 
 	/* Set the ASID. */
 	pteh |= get_asid() << PTEH_ASID_SHIFT;