ixgbe: cleanup error checking in ixgbe_identify_sfp_module_generic()

This patch replaces instances where a return code from i2c operations
were checked against a list of error codes with a much simpler
if ( status != 0 ) check.

Some whitespace cleanups included.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>