can: sja1000: add documentation for Technologic Systems version

This commit adds documentation for the Technologic Systems version of
SJA1000. The difference with the NXP version is in the way the registers
are accessed.

Signed-off-by: Damien Riegel <damien.riegel@savoirfairelinux.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Documentation/devicetree/bindings/net/can/sja1000.txt

@@ -2,7 +2,7 @@ Memory mapped SJA1000 CAN controller from NXP (formerly Philips)
 
 Required properties:
 
-- compatible : should be "nxp,sja1000".
+- compatible : should be one of "nxp,sja1000", "technologic,sja1000".
 
 - reg : should specify the chip select, address offset and size required
 	to map the registers of the SJA1000. The size is usually 0x80.
@@ -14,6 +14,7 @@ Optional properties:
 
 - reg-io-width : Specify the size (in bytes) of the IO accesses that
 	should be performed on the device.  Valid value is 1, 2 or 4.
+	This property is ignored for technologic version.
 	Default to 1 (8 bits).
 
 - nxp,external-clock-frequency : Frequency of the external oscillator