[CRIU] zdtm test build failure on s390x (s390x_regs_check.c)

[Adrian Reber]

When running 'make zdtm' on s390x it fails on my RHEL kernel with:

make[3]: Leaving directory `/tmp/criu/test/zdtm/lib'
 CC        s390x_regs_check.o
s390x_regs_check.c: In function ‘util_hexdump_grp’:
s390x_regs_check.c:214:7: error: ‘ptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
   ptr += sprintf(ptr, "%02x", buf[i]);
       ^
cc1: all warnings being treated as errors
make[2]: *** [s390x_regs_check.o] Error 1
make[2]: Leaving directory `/tmp/criu/test/zdtm/static'

		Adrian