net: fec: Remove unneeded use of IS_ERR_VALUE() macro

There is no need to use the IS_ERR_VALUE() macro for checking
the return value from pm_runtime_* functions.

Just do a simple negative test instead.

The semantic patch that makes this change is available
in scripts/coccinelle/api/pm_runtime.cocci.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>