i40e: fix code style

i40e: fix code style

Rename some local variables to express more accurately
and briefly. Fix several code style issues reported by
checkpatch.pl. Line warpping for some source lines which
has more than 80 characters, and merge lines together for
those source lines which does not need any line wrapping
actually. Add macros for numeric or calculating memory
sizes.

Signed-off-by: Helin Zhang <helin.zhang@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>