remoteproc: imx_dsp_rproc: Fix NULL vs IS_ERR() bug in imx_dsp_rproc_add_carveout()

remoteproc: imx_dsp_rproc: Fix NULL vs IS_ERR() bug in imx_dsp_rproc_add_carveout()

The devm_ioremap_resource_wc() function never returns NULL, it returns
error pointers.  Update the error checking to match.

Fixes: 67a7bc7f0358 ("remoteproc: Use of_reserved_mem_region_* functions for "memory-region"")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Iuliana Prodan <iuliana.prodan@nxp.com>
Link: https://lore.kernel.org/r/aSf6OerBbPcxBUVt@stanley.mountain
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>