staging: fsl-mc/dpio: Fix incorrect comparison

For some dpio functions, a cpu id parameter value of -1 is
valid and means "any". But when trying to validate this param
value against an upper limit, in this case num_possible_cpus(),
we risk obtaining the wrong result due to an implicit cast.

Avoid an incorrect check result by explicitly comparing the
cpu id with the "any" value before verifying the upper bound.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>