thinkpad-acpi: fix default brightness_mode for R50e/R51

thinkpad-acpi: fix default brightness_mode for R50e/R51

According to a report, the R50e wants EC-based brightness control,
even if it uses an Intel GPU.  The current driver default was reported
to not work at all.

This bug can be worked around by the "brightness_mode=3" module
parameter.

Change the default of the R50e and R51 2xxx models (which use the same
EC firmware, 1V) to TPACPI_BRGHT_Q_EC, but keep TPACPI_BRGHT_Q_ASK set
for now, as I'd like to get more reports.

This fixes a regression caused by commit
59fe4fe34d7afdf63208124f313be9056feaa2f4,
"thinkpad-acpi: fix incorrect use of TPACPI_BRGHT_MODE_ECNVRAM"

Kernel 2.6.31 also needs this fix.

Reported-by: Ferenc Wagner <wferi@niif.hu>
Tested-by: Ferenc Wagner <wferi@niif.hu>
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: stable@kernel.org