ARM: dts: imx7d-sdb: add rev-a board support

Current imx7d-sdb.dts has some incorrect settings about
Rev-A and Rev-B boards, some of the settings are based on
Rev-A board but some are based on Rev-B board, clean up it
by adding i.MX7D SDB Rev-A board support, make default
imx7d-sdb.dts for Rev-B board as usual, and introduce
imx7d-sdb-reva.dts for Rev-A board. Below are the affected
differences of Rev-A and Rev-B board:

                Rev-A           Rev-B
USB_OTG2_PWR:   UART3_CTS_B     GPIO1_IO07
ENET_EN_B:      None            GPIO1_IO04
TP_INT_B:       EPDC_DATA13     EPDC_BDR1

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>