greybus: interface: Mode switch takes over a second

Mode switch takes just over a second to complete and the current timeout
of one second isn't sufficient.

Mode-switch logs from EVT 1.5:

[   56.709082] gb-firmware 1-3.3.1: Requested firmware package 'ara_00000126_00001002_fffe0001_ff980067_03.tftf'
[   57.003968] gb_control_mode_switch_operation: 176
[   58.041616] greybus 1-3.3: mode switch detected

Increase the timeout to two seconds.

Tested with EVT 1.5 with gpbridge-test module.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Tested-by: Karthik Ravi Shankar <karthikrs@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>