usb: fix sysjump
usb: fix sysjump

Ensure that we can re-etablish a proper USB communication after a
sysjump by properly disabling the USB stack before jumping.
So the host sees a USB disconnection and can properly re-initialize the
device when it re-appears.

Signed-off-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

BRANCH=samus
BUG=none
TEST=On Twinkie, use the "sysjump RW" command on the USB console
and see the prompt coming back after a few seconds.

Change-Id: Iaf4498333eb4e7a1dda0f51ee8be19a0c9f10349
Reviewed-on: https://chromium-review.googlesource.com/239227
Reviewed-by: Anton Staaf <84531b4b964c017023781514a6665b71e84b32bc@chromium.org>
Tested-by: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>
Commit-Queue: Vincent Palatin <70a9964ec8fd10b0b08fcc8623c2add25ddf99ac@chromium.org>

fourier49/BIZ_EC,coreboot/chrome-ec,eatbyte/chromium-ec,fourier49/BIZ_EC,md5555/ec,mtk09422/chromiumos-platform-ec,fourier49/BIZ_EC,fourier49/BZ_DEV_EC,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,mtk09422/chromiumos-platform-ec,fourier49/BZ_DEV_EC,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,md5555/ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,akappy7/ChromeOS_EC_LED_Diagnostics,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,fourier49/BZ_DEV_EC,fourier49/BIZ_EC,mtk09422/chromiumos-platform-ec,eatbyte/chromium-ec,fourier49/BZ_DEV_EC,coreboot/chrome-ec,eatbyte/chromium-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec