USB: musb: JZ4770: Put ID pin debounce timer inside glue struct

This would allow supporting a theoretical device with two musb-based
controllers.
USB: musb: JZ4770: Cleaned up OTG ID pin debounce

Only use gpiolib calls, not hardware specific GPIO calls.
Take advantage of the dual flank emulation in the IRQ chip driver.
Don't bother to check for signal stability after the debounce interval
is over: if the signal is not stable, the interval was set too short.
MIPS: JZ4770: GCW0: Disable pull-up for USB OTG ID pin

Before, this was one in the musb glue, but to be consistent with other
drivers we do it in the board code instead.
fb: JZ4770: Don't update jz_clocks

I want to remove jz_clocks in the near future.
MIPS: JZ4770: Removed jz_clocks struct

It wasn't read by any driver.
mmc: JZ4770: Remove JZ_SYSTEM_AT_CARD changes in core

This config option was removed earlier (9cd75281), but this code using
it was overlooked.
ASoC: JZ4770: Implemented digital_mute callback
ASoC: JZ4770: Do not define set_sysclk callback

It is an optional operation and we have no use for it.
ASoC: JZ4770: Clean up widget names

Rename "Master Playback Volume" to "Headphone Playback Volume". The
"master" name was confusing, since this control is exclusive to the
headphone output: it doesn't affect line-out.

Renamed "DAC" to "PCM", since that seems to be the name users are most
familiar with. For the same reason, rename "Mux" to "Source".

Use "Capture Source" for the ADC mux, so alsamixer shows the special
capture source selection UI.

Removed "Capture" from line-in bypass and mic gain volume widgets,
since those belong to neither capture nor playback since their output
can be routed around both the ADC and the DAC.

Shorten "Microphone" to "Mic" for readability in limited space.
Made use of spaces consistent ("Linein" -> "Line In" etc).
Use "In" instead of "Input" consistently.
ASoC: JZ4770: GCW0: Set up actual board DAPM routes

The previous routes were still partially copied from the Pisces board
and did not match the GCW Zero.
ASoC: JZ4770: Fix DAPM route for Line In

The route should go through Line In Bypass, otherwise this block gets
powered down when listening to the radio and the bypass volume control
doesn't work.