remoteproc: Mark wc-ioremap carveouts as iomem

Carveouts registered through the shared wc-ioremap helper are backed by
I/O memory, but rproc_da_to_va() only reports that to its callers when
mem->is_iomem is set on the carveout.

Without that flag, the remoteproc ELF loader and coredump paths can
fall back to normal memcpy()/memset() accessors instead of the I/O
helpers used for iomapped memory.

Mark shared wc-ioremap carveouts as iomem so the framework uses the
proper memcpy_toio(), memset_io(), and memcpy_fromio() accessors for
these regions.

Signed-off-by: Ben Levinsky <ben.levinsky@amd.com>
Tested-by: Peng Fan <peng.fan@nxp.com> #i.MX8MP-EVK
Link: https://lore.kernel.org/r/20260529021637.2077602-4-ben.levinsky@amd.com
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

drivers/remoteproc/remoteproc_internal.h

@@ -136,6 +136,7 @@ static inline int rproc_mem_entry_ioremap_wc(struct rproc *rproc,
 	}
 
 	mem->va = (__force void *)va;
+	mem->is_iomem = true;
 
 	return 0;
 }