ixgbe: use IS_ENABLED() instead of checking for built-in or module

ixgbe: use IS_ENABLED() instead of checking for built-in or module

Orabug: 24568240

The IS_ENABLED() macro checks if a Kconfig symbol has been enabled either
built-in or as a module, use that macro instead of open coding the same.

Using the macro makes the code more readable by helping abstract away some
of the Kconfig built-in and module enable details.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit ee58c1149e2bba6043e31f736f6f6136562758ac)
Signed-off-by: Brian Maly <brian.maly@oracle.com>