Coding guideline: Fixing code violations for 21.13 Rule

Any value passed to a function in <ctype.h> shall be
representable as an unsigned char or be the value EOF.

So changed type of variable to unsigned char.

Signed-off-by: Spoorthy Priya Yerabolu <[email protected]>

Author: yerabolu

lib/os/cbprintf_complete.c

@@ -257,7 +257,7 @@ struct conversion {
 	bool pad_fp: 1;
 
 	/** Conversion specifier character */
-	char specifier;
+	unsigned char specifier;
 
 	union {
 		/** Width value from specification.

subsys/logging/log_minimal.c

@@ -39,7 +39,7 @@ static void minimal_hexdump_line_print(const char *data, size_t length)
 
 	for (size_t i = 0; i < HEXDUMP_BYTES_IN_LINE; i++) {
 		if (i < length) {
-			char c = data[i];
+			unsigned char c = data[i];
 
 			printk("%c", isprint((int)c) ? c : '.');
 		} else {