layerscape: kernel: enable MC userspace support

Management Complex (MC) userspace support is required for userspace
helpers working with DPAA2 objects exported by the Management Complex BUS.

Without it, there is the error:

```
root@OpenWrt:/# ls-addni dpmac.1
error: Did not find a device file
Restool wrapper scripts only support the latest major MC version
that currently is MC10.x. Use with caution.
error: Did not find a device file
```

This patch fixes it.

Suggested-by: Alexandra Alth <alexandra@alth.de>
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
(cherry picked from commit d04d6a8)

target/linux/layerscape/armv8_64b/config-5.15

@@ -291,7 +291,7 @@ CONFIG_FSL_GUTS=y
 CONFIG_FSL_IFC=y
 CONFIG_FSL_MC_BUS=y
 CONFIG_FSL_MC_DPIO=y
-# CONFIG_FSL_MC_UAPI_SUPPORT is not set
+CONFIG_FSL_MC_UAPI_SUPPORT=y
 # CONFIG_FSL_PPFE is not set
 # CONFIG_FSL_PPFE_UTIL_DISABLED is not set
 # CONFIG_FSL_QMAN_TEST is not set