[ARM] amba: fix amba device resources

AMBA device resources were being reported as:

10004000-10004fff : <BAD>

This is because dev_name() was returning NULL prior to device_register.
Ensure that the struct device is properly initialized, and the name is
set before adding it to the device tree.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>