doc: describe generation of SMBIOS table

SMBIOS is not x86 specific. So we should have an architecture independent
page describing it.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/doc/develop/index.rst b/doc/develop/index.rst
index 9714887..93ebfa4 100644
--- a/doc/develop/index.rst
+++ b/doc/develop/index.rst
@@ -22,6 +22,7 @@
    makefiles
    menus
    printf
+   smbios
    uefi/index
    version