drivers: nrf_qspi_nor: Refactor deactivation and locking access to QSPI

After integration of nrfx 3.2.0, it is no longer needed to deinitialize
the nrfx_qspi driver to avoid increased power consumption when the QSPI
peripheral is idle. Now it is enough to call `nrfx_qspi_dectivate()`
when a given operation is done. The driver will automatically activate
the QSPI peripheral again when a next operation is requested.

This commit applies the following changes:
- `qspi_device_init` and `qspi_device_uninit` functions are replaced
  by `qspi_acquire` and `qspi_release`, respectively; those handle
  exclusive access to the QSPI peripheral and deactivation of it or
  runtime device power management
- locking is removed from `qspi_send_cmd` as it is the resposibility
  of the caller of that function
- `trans_lock` and `trans_unlock` functions are removed together with
  the related semaphore as they are no longer needed
- checking of input parameters is moved from `qspi_erase` to its
  caller, `qspi_nor_erase`
- `qspi_nor_pm_action` is refactored to properly handle locking of
  the QSPI peripheral; checking of the `xip_enabled` flag is removed
  from that function as now the call to `pm_device_is_busy()` covers
  that (when XIP is enabled, the device is kept indicated as busy)

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>