spi: spi-fsl-dspi: restrict register range for regmap access

spi: spi-fsl-dspi: restrict register range for regmap access

DSPI registers are NOT continuous, some registers are reserved and
accessing them from userspace will trigger external abort, add regmap
register access table to avoid below abort.

  For example on S32G:

  # cat /sys/kernel/debug/regmap/401d8000.spi/registers

  Internal error: synchronous external abort: 96000210 1 PREEMPT SMP
  ...
  Call trace:
  regmap_mmio_read32le+0x24/0x48
  regmap_mmio_read+0x48/0x70
  _regmap_bus_reg_read+0x38/0x48
  _regmap_read+0x68/0x1b0
  regmap_read+0x50/0x78
  regmap_read_debugfs+0x120/0x338

Fixes: 1acbdeb92c87 ("spi/fsl-dspi: Convert to use regmap and add big-endian support")
Co-developed-by: Xulin Sun <xulin.sun@windriver.com>
Signed-off-by: Xulin Sun <xulin.sun@windriver.com>
Signed-off-by: Larisa Grigore <larisa.grigore@nxp.com>
Signed-off-by: James Clark <james.clark@linaro.org>
Link: https://patch.msgid.link/20250522-james-nxp-spi-v2-1-bea884630cfb@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>