mfd: intel_quark_i2c_gpio: Revert "Constify static struct resources"

The structures are used as place holders, so they are modified at run-time.
Obviously they may not be constants.

  BUG: unable to handle page fault for address: d0643220
  ...
  CPU: 0 PID: 110 Comm: modprobe Not tainted 5.11.0+ #1
  Hardware name: Intel Corp. QUARK/GalileoGen2, BIOS 0x01000200 01/01/2014
  EIP: intel_quark_mfd_probe+0x93/0x1c0 [intel_quark_i2c_gpio]

This partially reverts the commit c4a164f4.

While at it, add a comment to avoid similar changes in the future.

Fixes: c4a164f4 ("mfd: Constify static struct resources")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Tested-by: Tong Zhang <ztong0001@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>