Input: atkbd - fix multi-byte scancode handling on reconnect

On resume from suspend there is a possibility for multi-byte scancodes
to be handled incorrectly. atkbd_reconnect disables the processing of
scancodes in software by calling atkbd_disable, but the keyboard may
still be active because no disconnect command was sent. Later, software
handling is re-enabled. If a multi-byte scancode sent from the keyboard
straddles the re-enable, only the latter byte(s) will be handled.

In practice, this leads to cases where multi-byte break codes (ex. "e0
4d" - break code for right-arrow) are misread as make codes ("4d" - make
code for numeric 6), leading to one or more unwanted, untyped characters
being interpreted.

The solution implemented here involves sending command f5 (reset
disable) to the keyboard prior to disabling software handling of codes.
Later, the command to re-enable the keyboard is sent only after we are
prepared to handle scancodes.

Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>