OMAP4 clock: drop the ALWAYS_ENABLED clock flag

Get rid of the ALWAYS_ENABLED clock flag - it doesn't actually do anything.
(The OMAP4 clock autogeneration scripts have been updated accordingly.)

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Rajendra Nayak <rnayak@ti.com>
Cc: Benoît Cousson <b-cousson@ti.com>