tools/power/cpupower: fix 64bit detection when cross-compiling

When cross-compiling cpupower, 64bit detection is done with the host
compiler instead of the cross-compiler and libcpupower.so.0 ends up in
/usr/lib64 instead of /usr/lib for 32bit target.  Fix this by moving
64bit detection after CC is defined.

Signed-off-by: Sébastien Szymanski <sebastien.szymanski@armadeus.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>