gpiolib: Lower verbosity when allocating hierarchy irq

gpiolib: Lower verbosity when allocating hierarchy irq

In the current codes, the following 3 lines would be output to
the console for each irq line.
  gpio gpiochip0: (gpio_thunderx): allocate IRQ 10, hwirq 0
  gpio gpiochip0: (gpio_thunderx): found parent hwirq 245784
  gpio gpiochip0: (gpio_thunderx): alloc_irqs_parent for 10 parent hwirq 245784

In general, there are about tens of irq lines for each gpio chip,
and then it would emit so many insignificant log in the boot process.
These infos are more suitable for the dbg purpose. So change these
to the dbg level. With this change, about 200 lines are suppressed
on my Marvell cn96xx board.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Link: https://lore.kernel.org/r/20200120095625.25164-1-haokexin@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>