parisc: lasi: Initialize LASI driver via arch_initcall()

Move initialization code for LASI out of the GSC driver.
Since ASP and WAX have been moved in previous commits,
the GSC driver is now just a driver which provides library
functions for LASI, ASP and WAX and as such doesn't need
an own initialization function any longer.

Signed-off-by: Helge Deller <deller@gmx.de>