ARM: dts: am437x-gp: Add dcan support

Add DCAN support for AM437x GP EVM with both DCAN instances.

[Roger Q] Updated output pin to not use pull up.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Roger Quadros <rogerq@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>