internal: avoid sign extension of Statfs_t.Type on 32 bit arches
internal: avoid sign extension of Statfs_t.Type on 32 bit arches

Statfs_t.Type differs in size between 32 and 64 bit platforms:

    type Statfs_t struct {
        Type    int32
        ...
    }

    type Statfs_t struct {
        Type    int64
        ...
    }

This is a problem since the bpfFSType constant we want to compare
against is a negative number when intepreted as an int32. Therefore the
conversion to uint64 yields an invalid result due to sign extension.

Account for this difference by casting via uint32 on 32 bit arches.

Fixes #726

cilium/ebpf,cilium/ebpf