external/LinuxBoot: Kconfig defaults to systemboot

In addition to change CB:40316 this commit proposes a change of default
behavior inside of the LinuxBoot toolchain.

Currently the defaults build a LinuxBoot payload which boots into the
u-root shell and waits for input. In fact it does not deliver any
bootloader with it, but the build image is on the other hand rather
small.

This commit changes the defaults in a way that the LinuxBoot
bootloader will actually be able to boot a local or remote system image.
In consequence the build payload size is rather big, but accepted for a
working out-of-the-box startup behavior.

See discussion on that topic in the above mentioned change.

Signed-off-by: Patrik Tesarik <mail@patrik-tesarik.de>
Change-Id: Ieaba7e523aef10c467a8bea29ae323e22324b225
Reviewed-on: https://review.coreboot.org/c/coreboot/+/40527
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/payloads/external/LinuxBoot/Kconfig b/payloads/external/LinuxBoot/Kconfig
index edd4779..8836353 100644
--- a/payloads/external/LinuxBoot/Kconfig
+++ b/payloads/external/LinuxBoot/Kconfig
@@ -262,10 +262,10 @@
 
 choice
 	prompt "Choose a specific bootloader"
-	default SPECIFIC_BOOTLOADER_NONE
+	default SPECIFIC_BOOTLOADER_SYSTEMBOOT
 	help
 	  Specify a bootloader which starts after u-root init. It will be a symlink
-	  to /bin/uinit. Default: None
+	  to /bin/uinit. Default: systemboot
 
 config SPECIFIC_BOOTLOADER_NONE
 	bool "none"