pipeline: fix table entry read

pipeline: fix table entry read

The rte_swx_pipeline_table_entry_read() function is used to read from
a character string a table entry that is to be added to the table,
deleted from the table or set as the default entry of the table.
Addition needs both the match and the part of the entry, deletion
ignores the action part, while the default set ignores the match part,
hence the need to make both the match and the action part optional.
The logic for skipping the match or the action part was broken, hence
the current fix.

Fixes: b32c0a2c5e4c ("pipeline: add SWX table update high level API")
Cc: stable@dpdk.org
Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
Signed-off-by: Venkata Suresh Kumar P <venkata.suresh.kumar.p@intel.com>
Signed-off-by: Churchill Khangar <churchill.khangar@intel.com>