mtd: cfi_cmdset_0001: Fix exception handling in cfi_intelext_setup()

[Markus Elfring]

>> The label “setup_err” was used to jump to another pointer check despite of
>> the detail in the implementation of the function “cfi_intelext_setup”
>> that it was determined already that a corresponding variable contained
>> a null pointer because of a failed memory allocation.
>
> Can you please rephrase the commit log? It is super hard to understand.
Which wording variant would you find nicer for provided information?

* used jump targets

* null pointer assignments


Regards,
Markus