s390: Simple strcpy() to strscpy() conversions

Convert all strcpy() usages to strscpy() where the conversion means
just replacing strcpy() with strscpy(). strcpy() is deprecated since
it performs no bounds checking on the destination buffer.

Reviewed-by: Mikhail Zaslonko <zaslonko@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>