zipl: use `unsigned int` for the iteration variable
zipl: use `unsigned int` for the iteration variable

This fixes the false positive

CC      zipl/src/misc.o
misc.c: In function ‘misc_temp_dev’:
misc.c:313:27: warning: ‘%04d’ directive writing between 4 and 11 bytes into a region of size 5 [-Wformat-overflow=]
    sprintf(filename, "zipl%04d", retry);
                           ^~~~
misc.c:313:22: note: directive argument in the range [-2147483648, 999]
    sprintf(filename, "zipl%04d", retry);
                      ^~~~~~~~~~
misc.c:313:4: note: ‘sprintf’ output between 9 and 16 bytes into a destination of size 9
    sprintf(filename, "zipl%04d", retry);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

While at it, add an assertion that protects against a format-overflow,
e.g. if TEMP_DEV_MAX_RETRIES changes.

Reviewed-by: Jan Höppner <96138615ab4af0813785fa10d283f3d37eca3b78@linux.ibm.com>
Signed-off-by: Marc Hartmayer <7bafc8cd4e6394916d396e4f8cde69753be8d066@linux.ibm.com>
Signed-off-by: Jan Höppner <96138615ab4af0813785fa10d283f3d37eca3b78@linux.ibm.com>

ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools,ibm-s390-tools/s390-tools