CHROMIUM: md: dm-verity fixes chromeos needs

CHROMIUM: md: dm-verity fixes chromeos needs

This CL has all the changes that needed to be made to
the upstream version of dm-verity.
1. Notify
2. Same paramaters as the old version of dm-verity
3. Opening device by uuid

See CL 41206

At Mandeep's suggestion, I've modified the upstream version of
verity to accept the legacy parameters. This means we can move
to the upstream version of verity without making changes to
out build, install and signing scripts.

Results from platform_BootPerfServer/control.perfalerts
on a Lucas
			      baseline	CL
reboot_in_syslog		23	111
seconds_firmware_boot		30.86	30.75
seconds_kernel_to_chrome_exec	4.64	4.82
seconds_kernel_to_chrome_main	5.55	6.11
seconds_kernel_to_login		8.32	8.14
seconds_kernel_to_network	8.73	8.17
seconds_kernel_to_startup	1.63	1.72
seconds_kernel_to_startup_done	2.4	2.37
seconds_kernel_to_x_started	4.55	4.73
seconds_power_on_to_kernel	30.86	30.75
seconds_power_on_to_login	39.18	38.89 (30 sec wait for dev)

BUG=chromium-os:31803
TEST=platform_DMVerityCorruption, platform_DMVerityBitCorruption

Change-Id: Iaedc50bc679c931d77044589de1a305fcb5b0180
Signed-off-by: Paul Taysom <taysom@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/41468