lirc: added support for RaspberryPi GPIO

lirc_rpi: Use read_current_timer to determine transmitter delay. Thanks to jjmz and others
See: https://github.com/raspberrypi/linux/issues/525



lirc: Remove restriction on gpio pins that can be used with lirc

Compute Module, for example could use different pins

lirc_rpi: Add parameter to specify input pin pull

Depending on the connected IR circuitry it might be desirable to change the
gpios internal pull from it pull-down default behaviour. Add a module
parameter to allow the user to set it explicitly.

Signed-off-by: Julian Scheel <julian@jusst.de>