arm-bsp/n1sdp: Add support for Kernel PREEMPT_RT with linux-linaro-arm-rt

Add N1SDP settings and configurations for the kernel with PREEMPT_RT support
using the linux-linaro-arm-rt recipe.

Also, change linux-linaro-arm-n1sdp.inc to enable sharing commom patches for
N1SDP when building linux-linaro-arm or linux-linaro-arm-rt.

Change-Id: I101b2e6ffefa4f908389110048778aaf5226d5d0
Issue-Id: SCM-1653
Signed-off-by: Diego Sueiro <diego.sueiro@arm.com>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm-bsp/recipes-kernel/linux/arm-platforms-kmeta/bsp/arm-platforms/n1sdp/n1sdp-preempt-rt.scc

@@ -0,0 +1,6 @@
+define KMACHINE n1sdp
+define KTYPE preempt-rt
+define KARCH arm64
+
+kconf non-hardware ktypes/developer/developer.cfg
+kconf non-hardware ktypes/preempt-rt/preempt-rt.cfg

meta-arm-bsp/recipes-kernel/linux/linux-linaro-arm-n1sdp.inc

@@ -1,4 +1,4 @@
-FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}-5.4:"
+FILESEXTRAPATHS_prepend := "${THISDIR}/linux-linaro-arm-5.4:"
 
 SRC_URI_append = " \
     file://0001-TMP-iommu-arm-smmu-v3-Ignore-IOPF-capabilities.patch \
@@ -21,3 +21,11 @@ KBUILD_DEFCONFIG = "defconfig"
 KCONFIG_MODE = "--alldefconfig"
 
 COMPATIBLE_MACHINE = "n1sdp"
+
+# RT kernel machine description
+FILESEXTRAPATHS_prepend_pn-linux-linaro-arm-rt := "${THISDIR}:"
+SRC_URI_append_pn-linux-linaro-arm-rt = " file://arm-platforms-kmeta;type=kmeta;name=arm-platforms-kmeta;destsuffix=arm-platforms-kmeta"
+
+# Since we use the intree defconfig and the preempt-rt turns off some configs
+# do_kernel_configcheck will display warnings. So, lets disable it.
+KCONF_AUDIT_LEVEL_pn-linux-linaro-arm-rt = "0"