Add a small delay before flushing the serial line.
Add a small delay before flushing the serial line.

Sometimes there are a few garbages bytes received before the preamble
bytes. This typically happens when trying to download again after a
failed attempt. However trying to flush them immediately after opening
the serial port doesn't work.

Poltsi/libdivecomputer-vms,glance-/libdivecomputer,henrik242/libdivecomputer,venkateshshukla/libdivecomputer,josh-wambua/libdivecomputer,venkateshshukla/libdivecomputer,glance-/libdivecomputer,henrik242/libdivecomputer,josh-wambua/libdivecomputer