Documentation: Remove remaining useless reference to acpi_fake_ecdt

>From commit cd8c93a4:

"Similar functionality was turned on by acpi_fake_ecdt=1 command line
before. Now it is on all the time."

Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>