i2c-pxa2xx: pass of_node from platform driver to adapter and publish

the of_node will auto-publish devices which are added to the device
tree.

Commit 925bb9c6 aka ("of/i2c: Fix module load order issue caused by
of_i2c.c) moved the of_i2c_register_devices() function from the i2c core
back to the drivers. This patch does the same thing for the pxa driver.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Dirk Brandewie <dirk.brandewie@gmail.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>