Revert "ANDROID: fix type of sysinfo.uptime"

This reverts commit b4848eec05bc1325b4ea9fbdc5215a090a330617.

Only the bionic sysinfo tests cared about the sign of uptime, and
they have been modified to use a cast.  Remove the non-upstream
modification.

Bug: 188576657
Test: m USE_HOST_MUSL=true host-native
Change-Id: I92fd8884832532b6eb6b60ed8105bbb7994ec2f1
1 file changed