Recovery: uefi: Input char 'f' to force fastboot mode

[Leo-Yan]

UEFI booting images might not automatically run into fastboot mode, thus the sequential steps fail to flash images. This patch adds an extra option to set the console device node for Hikey960, and the script sends char 'f' to the console device so can force UEFI to run into fastboot mode.

The suggested command is as below:

sudo ./recovery-flash-uefi-prebuilt.sh -d \ -t /dev/ttyUSB0 -c /dev/ttyUSB1 ^^^ ^^^ USB/OTG port USB/UART port

Signed-off-by: Leo Yan leo.yan@linaro.org

[Leo-Yan]

@ric96 @hzhuang1 @docularxu , could you give a review for this patch? Thanks!

[Leo-Yan]

Thanks, @hzhuang1