Remove the unused cif_stack argument and add a protype in oplib_64.h
Commit ef3e035c ("sparc64: Fix register corruption in top-most
kernel stack frame during boot.") removed the cif_stack argument to
prom_cif init in the declaration at the caller site and the usage of it
within prom_cif_init, but not in the function signature of the function
itself.

This also fixes the following warning:
arch/sparc/prom/p1275.c:52:6: warning: no previous prototype for ‘prom_cif_init’

Fixes: ef3e035c ("sparc64: Fix register corruption in top-most kernel stack frame during boot.")
Link: https://lore.kernel.org/r/20240710094155.458731-3-andreas@gaisler.comSigned-off-by: Andreas Larsson <andreas@gaisler.com>