Add a common hex array in hexdump.c so everyone can use it.

Add a common hi/lo helper to avoid the shifting masking that is
done to get the upper and lower nibbles of a byte value.

Pull the pack_hex_byte helper from kgdb as it is opencoded many
places in the tree that will be consolidated.

Signed-off-by: Harvey Harrison <redacted>
---
 

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 4d46e29..792bf0a 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h

@@ -276,7 +276,17 @@ extern void print_hex_dump(const char *level, const char *prefix_str,
 				const void *buf, size_t len, bool ascii);
 extern void print_hex_dump_bytes(const char *prefix_str, int prefix_type,
 			const void *buf, size_t len);
-#define hex_asc(x)	"0123456789abcdef"[x]
+
+extern const char hex_asc[];
+#define hex_asc_lo(x)	hex_asc[((x) & 0x0f)]
+#define hex_asc_hi(x)	hex_asc[((x) & 0xf0) >> 4]
+
+static inline char *pack_hex_byte(char *buf, u8 byte)
+{
+	*buf++ = hex_asc_hi(byte);
+	*buf++ = hex_asc_lo(byte);
+	return buf;
+}