arm: allwinner: cir: Reduce verbosity

IR can be noisy in dmesg if it "receive" some unwanted data.
Add a tunable hw.aw_cir.debug to enable those message that are
only useful if one wants to debug the driver.

Sponsored by: Diablotin Systems
Differential Revision: https://reviews.freebsd.org/D30972
Reviewed by: ganbold
MFC after: 1 month