selftests/powerpc: remove unneeded semicolon

Eliminate the following coccicheck warning:
./tools/testing/selftests/powerpc/nx-gzip/gzfht_test.c:327:4-5: Unneeded
semicolon

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/1612780870-95890-1-git-send-email-yang.lee@linux.alibaba.com