trunks_send: fix compiling error of comparing int and uint_32.

This is specific to reef factory branch not from original CLs stack. It
seems the compile options here treated warning as error so can't compile
trunks_send without this fix.

BUG=b:73256785
TEST=Locally compile trunks_send succesfully.

Change-Id: I6403fd654c088db1fbd7113a7e5377e86acb510d
1 file changed