sonynwz: quirk for cpufreq broken driver

There was some redundancy between frequency_linux(cpu, true) and
current_scaling_frequency(), also I see no reason to compile the cpuinfo stuff
unconditionally and the scaling info only on DX since it was already printed
some partial scaling info anyway. Thus compile all the code unconditionally
and simplify the logic in the debug menu. Also avoid putting buffers of size
PATH_MAX on stack since it can be quite big and we only requires 64 bytes
for those paths.

On Sony NWZ, the cpu driver reports frequency in MHz instead of kHz thus we need
to make the cpuinfo code aware of that bug.

Change-Id: I61af45ab5f179ecc909b4841b9137a915a60193a

System -> Debug (Keep Out) -> View CPU stats

Will now show the current cpufreq scaling governor, minimum, current and
maximum cpufreq scaling frequency for each CPU.

This may be genric for Android kernel based devices but is only enabled
for iBasso Devices. Other maintainers may choose do adopt this.

Change-Id: I53e212f8707bf2abaa557e297293fb559ac37058

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31555 a1c6a512-1295-4272-9138-f99709370657

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31554 a1c6a512-1295-4272-9138-f99709370657

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31553 a1c6a512-1295-4272-9138-f99709370657

The new menu is very helpful on RaaA, but also shown in the sim. It shows
the process cpu usage, process' time stats (user,sys,real) and the cpu
frequency stats.

It uses a thread to sample the data, however the thread is not created
until the menu is visited for the first time.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@31364 a1c6a512-1295-4272-9138-f99709370657