mtd: cfi_cmdset_0002: consider version 1.4 as a valid primary extension version

The Spansion S29WS-P device family uses CFI version 1.4 [1].
Consider it as a valid version.

[1] http://www.spansion.com/Support/Datasheets/s29ws-p_00_a12_e.pdf



Signed-off-by: Guillaume LECERF <glecerf@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>