ath6kl: add tracing point for hif irqs

Add a tracing point for hif irq and dump the register content to user space.
This is in hif.c as we could use the same code also with SPI but, as ath6kl
doesn't SPI and most likely never will be, this is used just by SDIO so
name the trace point as ath6kl_sdio_irq to make it easier to manage filters.

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>