Increase Seac iostream timeout because of read-poll latency

[weppos]

SEAC Tablet over BLE (read-poll transport) shows
slow and variable command/response timing during
device_open and early packet exchange.

This commit raises the SEAC timeout to 3000ms
to reduce early false timeouts seen with shorter
values.

Examples of round-trips from the official vendor app
(on MacOS) that are also reflected on the BLE interaction using this lib:

req 117594.891 -> resp 117596.899 delta 2.008s
req 117602.959 -> resp 117604.967 delta 2.008s
req 117605.029 -> resp 117607.037 delta 2.008s
req 117607.099 -> resp 117609.108 delta 2.009s
req 117609.229 -> resp 117611.297 delta 2.068s

It's possible the latency is a limitation of the BLE implementation on Mac/iPhone devices.