e1000/base: remove useless return variables
e1000/base: remove useless return variables

Although this change should be optimized out by the compiler, just
return a constant directly rather than declare a variable.

Signed-off-by: Wenzhuo Lu <58cb9036bdff9a5412edc3b9f70e105ccf59954f@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk