Remove extra arguments to afs_syscall_call

Remove extra arguments to afs_syscall_call

Someone appears to have mistaken afs_syscall_call for
afs_syscall_pioctl, and passed rvp and CRED to afs_syscall_call on
solaris (afs_syscall_call always takes 6 arguments; afs_syscall_pioctl
takes various arguments depending on the platform). After
b1ff4a0b1115f5739c0365cc963189b1f931971f, this breaks the client build
on AFS_SUN5_ENV, but only because it added prototypes for
afs_syscall_call; it looks like it's always been wrong, but it was never
noticed.

Reviewed-on: http://gerrit.openafs.org/653
Tested-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Derrick Brashear <shadow@dementia.org>