event/cnxk: add option to configure getwork mode

event/cnxk: add option to configure getwork mode

Add devargs to configure the platform specific getwork mode.

CN9K getwork mode by default is set to use dual workslot mode.
Add option to force single workslot mode.
Example:
	--dev "0002:0e:00.0,single_ws=1"

CN10K supports multiple getwork prefetch modes, by default the
prefetch mode is set to none.
Add option to select getwork prefetch mode
Example:
	--dev "0002:1e:00.0,gw_mode=1"

Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
Signed-off-by: Shijith Thotton <sthotton@marvell.com>