meta-ethanolx: Add support for Legacy/EFI selector

AMD EthanolX CRB is a board with x86-64 CPU, which means it can support
both EFI and Legacy boot.
Add 'boot_type' PACKAGECONFIG option for the phosphor-settings-manager
package to support EFI/Legacy selector in the BMC boot override feature.
This setting is designed for the possibility of setting boot override
as:
- "PC compatible" boot (legacy)
- Extensible Firmware Interface Boot (EFI)

Change-Id: I173c5b439b929e80f3a106f5e7775862f889ee16
Signed-off-by: Konstantin Aladyshev <aladyshev22@gmail.com>
diff --git a/meta-amd/meta-ethanolx/recipes-phosphor/settings/phosphor-settings-manager_%.bbappend b/meta-amd/meta-ethanolx/recipes-phosphor/settings/phosphor-settings-manager_%.bbappend
new file mode 100644
index 0000000..ae55f69
--- /dev/null
+++ b/meta-amd/meta-ethanolx/recipes-phosphor/settings/phosphor-settings-manager_%.bbappend
@@ -0,0 +1 @@
+PACKAGECONFIG_append_ethanolx = " boot_type"