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>

arch/sh/mm/tlbflush_64.c

@@ -337,7 +337,7 @@ void local_flush_tlb_one(unsigned long asid, unsigned long page)
 	/*
 	 * Sign-extend based on neff.
 	 */
-	lpage = (page & NEFF_SIGN) ? (page | NEFF_MASK) : page;
+	lpage = neff_sign_extend(page);
 	match = (asid << PTEH_ASID_SHIFT) | PTEH_VALID;
 	match |= lpage;