pia35x: update default command line

- enable ext4 for rootfs
- mount rootfs read-only to allow easier boottime fsck
- make quiet default: use u-boot env variable "quiet" to change "output"

Signed-off-by: Björn Krombholz <b.krombholz@pironex.de>
pia35x: enable pull-ups for UART RX lines

- this is neccessary for ISL3330 RS232/RS485 IC and doesn't hurt for the
  other interfaces

Signed-off-by: Björn Krombholz <b.krombholz@pironex.de>
Merge branch 'pia-master' into pia35x-release