ofp-actions: Make union ofp_action more generic.

ofp-actions: Make union ofp_action more generic.

Make union ofp_action more generic by allowing it to be used for
all actions.  OFP_ACTION_ALIGN (which is 8, as the sizeof(union
ofp_action) used to be) is now used where sizeof union ofp_action
was used before.  On the same note, variable name 'n_actions' is
changed to 'max_actions' as the number of actions cannot be simply
divided when actions have various sizes.

Signed-off-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>