dt-bindings: nvmem: fixed-cell: increase bits start value to 31

dt-bindings: nvmem: fixed-cell: increase bits start value to 31

If NVMEM uses a data stride bigger than a byte, the starting bit of the
cell might be bigger than a byte (e.g. if the data comes in the second
byte of the 4-byte word). Allow the staring bit to be 8 or greater to
reflect such usecases.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20250411112251.68002-8-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>