ixgbe: cleanup code in ixgbe_identify_sfp_module_generic

This change cleans up several issues in ixgbe_identify_sfp_module_generic
including whitespace, redundant code, I2C EEPROM reads without exception
handling, and an if/elseif/else without braces.

Signed-off-by: Emil Tantilov <emil.s.tantilov@intel.com>
Tested-by: Stephen Ko <stephen.s.ko@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>