s390/compat: fix typo

Reported-by: NMichael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/compat_wrapper.c

 /*
- *  Compat sytem call wrappers.
+ *  Compat system call wrappers.
  *
  *    Copyright IBM Corp. 2014
  */