perf s390: Rework system call table creation by using syscall.tbl

Recently, s390 uses a syscall.tbl input file to generate its system call
table and unistd uapi header files.  Hence, update mksyscalltbl to use
it as input to create the system table for perf.

Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Thomas Richter <tmricht@linux.vnet.ibm.com>
Cc: linux-s390@vger.kernel.org
LPU-Reference: 1518090470-2899-4-git-send-email-brueckner@linux.vnet.ibm.com
Link: https://lkml.kernel.org/n/tip-bdyhllhsq1zgxv2qx4m377y6@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>