spi/pl022: fix dubious allocation staticize platform data

This removes some dubious allocation of a local chipinfo struct
in favor of a constant preset, tagging that one const revealed
further problems with platform data being modified so fixed up
these too.

Reported-by: Virupax Sadashivpetimath <virupax.sadashivpetimath@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>