UBUNTU: SAUCE: platform/x86: dell-uart-backlight: increase retry times

UBUNTU: SAUCE: platform/x86: dell-uart-backlight: increase retry times

BugLink: https://bugs.launchpad.net/bugs/1862885
From ODM, scalar takes some time to activate panel during booting up,
it can't respond the UART commands within 1 seconds.
So, we add retry and wait 2 seconds for the response. But sometimes it
still fails to read the response.
During the boot up time, it sometimes takes more than 2 seconds to respond
the first command, so we enlarge the retry timeout from 2 seconds to 5
seconds to make sure we get the first response from scalar.

Signed-off-by: AceLan Kao <acelan.kao@canonical.com>
Acked-By: You-Sheng Yang <vicamo.yang@canonical.com>
Acked-by: Anthony Wong <anthony.wong@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>