mtd: cfi_cmdset_0002: do not fail on no extended query table as they are both optional
After looking at AMD's CFI specification [1], both of the extended query
tables are optional. Thus, it looks like relying that at least one of
those tables exist is a bug in cfi_cmdset_0002.
This patch inverts the logic and checks for unlock function pointers before
exiting on error. This approach leaves place to add a call to a fixup
function to try to handle chips compatible with the early AMD specification
from 1995 [2].