mkefidisk: Always specify a root= kernel parameter
The current script only replaces an existing root= kernel parameter
which can result images created without a root= paremeter, even though
the script expects a target rootfs parameter.
Rather than replacing the root= parameter, delete the root= parameter if
it exists, then append an appropriate root= parameter.
Fixes [YOCTO 4035] mkefidisk.sh forgets to add root= parameter
Signed-off-by: Darren Hart <dvhart@linux.intel.com> Cc: Koen Kooi <koen@dominion.thruhere.net> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
