Replace int -> uint to avoid signed integer overflow

Replace int -> uint to avoid signed integer overflow

An example of such an error (should be compiled with DEBUG_SANITIZE):

runtime error: left shift of 1 by 31 places cannot be represented in
type 'int'

Signed-off-by: Rostislav Skudnov <rostislav@tuxera.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>