core/linux-sun4i: enable sunxi-ir

It was disabled in 7f2b3cf "core/linux-sun4i: config fixes", by the following hunk:

    -CONFIG_IR_SUN4I=m
    +# CONFIG_IR_SUNXI is not set

Seem to be working fine if enabled:

    [    1.552253] input: sunxi-ir as /devices/virtual/input/input0
    [    1.558300] IR Initial OK

/proc/bus/input/devices entry:

    I: Bus=0019 Vendor=0001 Product=0001 Version=0100
    N: Name="sunxi-ir"
    P: Phys=RemoteIR/input1
    S: Sysfs=/devices/virtual/input/input0
    U: Uniq=
    H: Handlers=sysrq rfkill kbd event0 
    B: PROP=0
    B: EV=3
    B: KEY=ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff fffffffe

Maybe it was disabled accidentally due to symbol name change?

Proposed commit re-enables it as a module.