OMAP4: clockdomain: bypass unimplemented wake-up dependency functions on OMAP4

Commit 56a6a19d ("omap2plus: prm:
Trvial build break fix for undefined reference to
'omap2_prm_read_mod_reg'") generates a lot of warnings on boot since
clockdomain functions that manipulate wake-up dependencies are not
implemented yet on OMAP4 for 2.6.38.  This patch bypasses the OMAP2/3
functions on OMAP4, which in turn avoids the warnings when the
functions would attempt to call the underlying OMAP2/3 PRCM functions.
A one-line warning is still logged from the clockdomain code that the
OMAP4 wake-up dependency code is not yet implemented.

A clockdomain wake-up and sleep dependency implementation for OMAP4
from Rajendra should be possible to merge during the 2.6.39 merge
window:

    http://www.mail-archive.com/linux-omap@vger.kernel.org/msg41748.html

    http://www.mail-archive.com/linux-omap@vger.kernel.org/msg42222.html



Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Cc: Rajendra Nayak <rnayak@ti.com>
Cc: Benoît Cousson <b-cousson@ti.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>