zipl: check array limits before indexing
zipl: check array limits before indexing

Resolves Cppcheck warning:
[zipl/boot/menu.c:126]: (style) Array index 'i' is used before limits check.

Cc: Stefan Haberland <9e6a0bb809a7918e8f27f36fc1281e79ae9e5bd0@de.ibm.com>
Cc: Peter Oberparleiter <db44112e0f7c7459f7ecb043f101f88a2e807d9f@de.ibm.com>
Signed-off-by: Jens Remus <9647a37a176c11c7fb6887065f43509d6f3a5d2d@linux.ibm.com>
Reviewed-by: Jan Höppner <96138615ab4af0813785fa10d283f3d37eca3b78@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