Fix detection of kernelroot with Yocto 2.5
Fix detection of kernelroot with Yocto 2.5

Resolves: LE-11673
Change-Id: Iaa9306ddcb085081a5d7163963ea749fdc5f6a6c

legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af