See http://blog.michael.kuron-germany.de/2011/03/patching-dsdt-in-recent-linux-kernels-without-recompiling/

Decompile the dsdt, patch it, and recompile again :

cat /sys/firmware/acpi/tables/DSDT > ~/dsdt/DSDT.dat
iasl -d DSDT.dat 
# patch it first, then recompile back
iasl -tc DSDT.dsl

The above give you a DSDT.aml, copy that to /boot/dsdt.aml, and create the /etc/grub.d/01_acpi file, run update-grub2

The section to modify in DSDT.dsl is :

Original:
Name (CPFS, Package (0x06)
{
0x64,
0x46,
0x3C,
0x32,
0x00,
0x00
})


My own version:
Name (CPFS, Package (0x06)
{
0x64,
0x46,
0x20,
0x10,
0x08,
0x00
})