cxl: Fix an error message

cxl: Fix an error message

'rc' is known to be 0 here.
Initialize 'rc' with the expected error code before using it.

While at it, avoid the affectation of 'rc' in a 'if' to make things more
obvious and linux style.

Fixes: f204e0b8cedd ("cxl: Driver code for powernv PCIe based cards for userspace access")
Acked-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://lore.kernel.org/r/fa2b2c9c72335ab4c3d5e6a33415e7f020b1d51b.1620243401.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>