[scudo] Fix reallocate for MTE. (#190086)

For MTE, we can't use the whole size or we might trigger a segfault.
Therefore, use the exact size when MTE is enabled or the exact usable
size parameter is true.

Also, optimize out the call to getUsableSize and use a simpler
calculation.

GitOrigin-RevId: 7c260d3966534031f9fe3a35b54887f6d979606d
1 file changed