driver: flash: mcux_flexspi_nor: Second attempt to fix is25lpXXX chips

This commit changes the implementation to distinguish between is25lpXXX
and is25lpXXXd. Using RDERP as in the original solution didn't work for
is25wpXXX chips and would cause a halt. This new implementation reads
the AutoBoot register instead, which is not present in is25lpXXX but
present in is25lpXXXd, is25wpXXX and is25wpXXXd.

Tested on:
- mimxrt1020-evk
- mimxrt1170-evk rev. A
- custom board with mimxrt1170 and is25lp128d

Signed-off-by: John Barbero Unenge <git@lsrkttn.com>