bus: fsl-mc: fsl-mc-allocator: Drop if block with always wrong condition

If fsl_mc_is_allocatable(mc_dev) evaluates to false, the driver won't
have bound to that device and then fsl_mc_allocator_remove() is never
called for that device. fsl_mc_allocator_remove() is the only caller of
fsl_mc_resource_pool_remove_device(), so the same check can be removed
from there.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Tested-by: Ioana Ciornei <ioana.ciornei@nxp.com> # sanity checks
Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Tested-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>