{linux, linux-headers}: default to 4.19.x

4.20.x is not a long term support kernel, but 4.19.x is (supported until end
2020):
https://www.kernel.org/category/releases.html

With the upcoming Buildroot 2019.02 release being a LTS release, default to
4.19.x instead.

Notice: The userspace API breakage in net_stamp.h causing build failures has
now been fixed in 4.19.14 by commit e4a2ffe9029fd (net: Use
__kernel_clockid_t in uapi net_stamp.h)

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
[Thomas: add comment in linux/Config.in and
package/linux-headers/Config.in.host so that we don't mistakenly bump
to 4.20+.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

linux/Config.in

@@ -29,8 +29,10 @@ config BR2_LINUX_NEEDS_MODULES
 choice
 	prompt "Kernel version"
 
+# We are intentionally staying at 4.19 for the next Buildroot LTS
+# release (2019.02)
 config BR2_LINUX_KERNEL_LATEST_VERSION
-	bool "Latest version (4.20)"
+	bool "Latest version (4.19)"
 
 config BR2_LINUX_KERNEL_LATEST_CIP_VERSION
 	bool "Latest CIP SLTS version (v4.4.154-cip28)"
@@ -120,7 +122,7 @@ endif
 
 config BR2_LINUX_KERNEL_VERSION
 	string
-	default "4.20.1" if BR2_LINUX_KERNEL_LATEST_VERSION
+	default "4.19.14" if BR2_LINUX_KERNEL_LATEST_VERSION
 	default "v4.4.154-cip28" if BR2_LINUX_KERNEL_LATEST_CIP_VERSION
 	default BR2_LINUX_KERNEL_CUSTOM_VERSION_VALUE \
 		if BR2_LINUX_KERNEL_CUSTOM_VERSION

package/linux-headers/Config.in.host

@@ -6,7 +6,9 @@ config BR2_PACKAGE_HOST_LINUX_HEADERS
 choice
 	prompt "Kernel Headers"
 	default BR2_KERNEL_HEADERS_AS_KERNEL if BR2_LINUX_KERNEL
-	default BR2_KERNEL_HEADERS_4_20
+	# We are intentionally staying at 4.19 for the next Buildroot
+	# LTS release (2019.02)
+	default BR2_KERNEL_HEADERS_4_19
 	help
 	  Select the kernel version to get headers from.