V4L/DVB (4763): Pvrusb2: Implement IR reception for 24xxx devices

V4L/DVB (4763): Pvrusb2: Implement IR reception for 24xxx devices

Unlike 29xxx devices, the 24xxx model series does not have a dedicated
I2C device for reception of IR codes.  Instead IR is handled directly
by the FX2 microcontroller and the results are communicated via
commands to the FX2.  Rather than implement a whole new IR reception
pathway for 24xxx devices, this changeset instead emulates the
presence of the 29xxx device's I2C based IR receiver by intercepting
commands to that chip and issuing appropriate FX2 commands to do the
needed action.  This has the result of allowing all the usual IR
frameworks (ir-kbd-i2c or lirc) to continue working unmodified for
24xxx devices.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>