rename superh port to "sh" for consistency

linux, gcc, etc. all use "sh" as the name for the superh arch. there
was already some inconsistency internally in musl: the dynamic linker
was searching for "ld-musl-sh.path" as its path file despite its own
name being "ld-musl-superh.so.1". there was some sentiment in both
directions as to how to resolve the inconsistency, but overall "sh"
was favored.

configure

@@ -229,7 +229,7 @@ x86_64*) ARCH=x86_64 ;;
 mips-*|mipsel-*) ARCH=mips ;;
 microblaze-*) ARCH=microblaze ;;
 powerpc-*) ARCH=powerpc ;;
-sh-*) ARCH=superh ;;
+sh-*) ARCH=sh ;;
 unknown) fail "$0: unable to detect target arch; try $0 --target=..." ;;
 *) fail "$0: unknown or unsupported target \"$target\"" ;;
 esac
@@ -421,7 +421,7 @@ fi
 test "$ARCH" = "microblaze" && trycppif __MICROBLAZEEL__ "$t" \
 && SUBARCH=${SUBARCH}el
 
-test "$ARCH" = "superh" && trycppif __LITTLE_ENDIAN__ "$t" \
+test "$ARCH" = "sh" && trycppif __LITTLE_ENDIAN__ "$t" \
 && SUBARCH=${SUBARCH}el
 
 test "$SUBARCH" \