tiny-printf: Always print zeroes

At present this does not print zero values in numeric format (hex and
decimal). Add a special case for this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Stefan Roese <sr@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>

lib/tiny-printf.c

@@ -82,13 +82,21 @@ int vprintf(const char *fmt, va_list va)
 					num = -(int)num;
 					out('-');
 				}
-				for (div = 1000000000; div; div /= 10)
-					div_out(&num, div);
+				if (!num) {
+					out_dgt(0);
+				} else {
+					for (div = 1000000000; div; div /= 10)
+						div_out(&num, div);
+				}
 				break;
 			case 'x':
 				num = va_arg(va, unsigned int);
-				for (div = 0x10000000; div; div /= 0x10)
-					div_out(&num, div);
+				if (!num) {
+					out_dgt(0);
+				} else {
+					for (div = 0x10000000; div; div /= 0x10)
+						div_out(&num, div);
+				}
 				break;
 			case 'c':
 				out((char)(va_arg(va, int)));