[MIPS] Lasat: sysctl fixup

LASAT's sysctl interface was broken, it failed a check during boot because
a single entry had a sysctl number and the rest were unnumbered. When I
fixed it I noticed that the whole sysctl file needed a spring clean, it was
using mutexes where it wasn't needed (it's only needed to protect during
writes to the EEPROM), so I moved that stuff out and generally cleaned the
whole thing up.

So now, LASAT's sysctl/proc interface is working again.

Signed-off-by: Thomas Horsten <thomas@horsten.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>