kernel: Release Linux v4.4.92-openpower1

In particular pick up a fix in the NVMe driver:
6d1400b0 "nvme: protect against simultaneous shutdown invocations"

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
diff --git a/openpower/configs/openpower_mambo_defconfig b/openpower/configs/openpower_mambo_defconfig
index e3be3ad..cbec4ed 100644
--- a/openpower/configs/openpower_mambo_defconfig
+++ b/openpower/configs/openpower_mambo_defconfig
@@ -31,7 +31,7 @@
 BR2_ROOTFS_POST_BUILD_SCRIPT="../openpower/scripts/fixup-target-var"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_VERSION=y
-BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.4.87"
+BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE="4.4.92"
 BR2_KERNEL_HEADERS_4_4=y
 BR2_BINUTILS_VERSION_2_26_X=y
 BR2_LINUX_KERNEL_PATCH="$(BR2_EXTERNAL)/linux"