src: Use 1U for bit shifting

src: Use 1U for bit shifting

In a few places we take 1 and shift it left repeatedly. So much
that it won't longer fit into signed integer. The problem is that
this is undefined behaviour. Switching to 1U makes us stay within
boundaries.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Tim Wiederhake <twiederh@redhat.com>