cpu: Quieten OS endian switch messages
cpu: Quieten OS endian switch messages

Users see these when loading an OS from Petitboot:

 [  119.486794100,5] OPAL: Switch to big-endian OS
 [  120.022302604,5] OPAL: Switch to little-endian OS

Which is expected and doesn't provide any information the user can act
on. Switch them to PR_INFO so they still appear in the log, but not on
the serial console.

Signed-off-by: Joel Stanley <4816dabf8db1bc6cac35b3a24cab2ff844b5b0c7@jms.id.au>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.ibm.com>

shenki/skiboot,stewart-ibm/skiboot,open-power/skiboot,legoater/skiboot,open-power/skiboot,legoater/skiboot,stewart-ibm/skiboot,stewart-ibm/skiboot,qemu/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,legoater/skiboot,legoater/skiboot,shenki/skiboot,open-power/skiboot,qemu/skiboot,qemu/skiboot,qemu/skiboot,open-power/skiboot,legoater/skiboot,shenki/skiboot,qemu/skiboot