powerpc/p1010rdb: Change flexcan compatible string

Change flexcan compatible string from "fsl,flexcan-v1.0"
to "fsl,p1010-flexcan" to match the device tree.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@freescale.com>
Signed-off-by: Andy Fleming <afleming@freescale.com>