[PA-RISC] Fix sys32_sysctl

When CONFIG_SYSCTL_SYSCALL isn't defined, do_sysctl doesn't exist and
we fail to link.  Fix with an ifdef, the same way sparc64 did.
Also add some minor changes to be more like sparc64.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
1 file changed