pc-bios/s390-ccw: size_t should be unsigned

"size_t" should be an unsigned type according to the C standard.
Thus we should also use this convention in the s390-ccw firmware to avoid
confusion. I checked the sources, and apart from one spot in libc.c, the
code should all be fine with this change.

Buglink: https://bugs.launchpad.net/qemu/+bug/1753437
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: Halil Pasic <pasic@linux.vnet.ibm.com>
Reviewed-by: Collin Walling <walling@linux.ibm.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

pc-bios/s390-ccw/libc.c

@@ -63,7 +63,7 @@ uint64_t atoui(const char *str)
  */
 char *uitoa(uint64_t num, char *str, size_t len)
 {
-    size_t num_idx = 1; /* account for NUL */
+    long num_idx = 1; /* account for NUL */
     uint64_t tmp = num;
 
     IPL_assert(str != NULL, "uitoa: no space allocated to store string");

pc-bios/s390-ccw/libc.h

@@ -12,7 +12,7 @@
 #ifndef S390_CCW_LIBC_H
 #define S390_CCW_LIBC_H
 
-typedef long               size_t;
+typedef unsigned long      size_t;
 typedef int                bool;
 typedef unsigned char      uint8_t;
 typedef unsigned short     uint16_t;