brcm47xx: swap also early boot console if necessary.

Some devices are using tty1 as the default console, also swap the early 
boot console in such case. This is needed for the WGT634U.

Thank you Russell for reporting this.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>


git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38794 3c298f89-4303-0410-b956-a3cf2f4a3e73