board: MCR3000: Remove update of non-existing e1-wan DT node

e1-wan device-tree node doesn't exist. Remove related update
to avoid following warning at startup:

	 Loading Device Tree to 007fa000, end 007ff951 ... OK
	Unable to update property /localbus/e1-wan:data-rate, err=FDT_ERR_NOTFOUND
	Unable to update property /localbus/e1-wan:channel-phase, err=FDT_ERR_NOTFOUND
	Unable to update property /localbus/e1-wan:rising-edge-sync-pulse, err=FDT_ERR_NOTFOUND

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: FRANJOU Stephane <stephane.franjou@csgroup.eu>