SFP matching is done by in order:
-vendor name, part number, serial
-vendor name, part number
-part number

If .config's entry (i.e. serial) is not empty match will happen only with
specific serial.

Additionally:
-Change default defines in Kconfig
-Update user manual with matching info
-Remove entry from wrs-todo about matching SFP vendor

Signed-off-by: Adam Wujek <adam.wujek@cern.ch>