cape: Add a simple cape for handling the uSD button.

Doesn't work ofcourse due to conflict with the HDMI.
tilcdc: Enable pinmux states

Things like the boot switch are on the LCD data pins.
Allows us to change pinmuxing on runtime.
beaglebone black: limit LDO3 to 1.8V

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>
capemgr: Implement disable overrides on the cmd line

Allow capes to be disabled on the kernel command line.

Signed-off-by: Pantelis Antoniou <panto@antoniou-consulting.com>