iwlwifi: mvm: revisit the NVM handling code

Fix a bug in nvm_read_section function if size of the section
is a multiple of 2K:

   - if the size of the section is *not* multiple of 2K,
   then we will have: read(2K) - return 2K ... read(2K) - return 2K
   read(2K) - return the rest (in bytes) and exit the while loop.
   - else, if the size of the section is a multiple of 2K,
   then we have: read(2K) - return 2K read(2K) - return 2K read(2K) -
   return 2K read(2K) - return 0 and exit the while with an error.

We should not return an error in the latter case, because it
might well be that the section was completely read.

Also, we try now to read all the sections as this is needed
for new devices.

Signed-off-by: Eran Harary <eran.harary@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>