HID: cp2112: Cleanups and refactorings

After I updated GPIO library for the case Benjamin has with CP2112, I have a brief look into the CP2112 driver itself.

From GPIO perspective it has two main (maitenance) issues:
- usage of ->to_irq() with IRQ chip present;
- having IRQ chip not immutable.

Besides that there are plenty small cleanups here and there. Hence this series.

Compile tested only.

Andy Shevchenko (12):
lib/string_choices: Add str_write_read() helper
HID: cp2112: Use str_write_read() and str_read_write()
HID: cp2112: Make irq_chip immutable
HID: cp2112: Switch to for_each_set_bit() to simplify the code
HID: cp2112: Don't call ->to_irq() explicitly
HID: cp2112: Remove dead code
HID: cp2112: Define maximum GPIO constant and use it
HID: cp2112: Define all GPIO mask and use it
HID: cp2112: Use BIT() in GPIO setter and getter
HID: cp2112: Use sysfs_emit() to instead of scnprintf()
HID: cp2112: Convert to DEVICE_ATTR_RW()
HID: cp2112: Use octal permissions

 drivers/hid/hid-cp2112.c       | 169 +++++++++++----------------------
 include/linux/string_choices.h |   1 +
 2 files changed, 58 insertions(+), 112 deletions(-)

2.40.0.1.gaa8946217a0b