bus: ocp2scp: SYNC2 value should be changed to 0x6

As per the TRMs of AM572x, OMAP4430, OMAP4460, OMAP543x, the value of
SYNC2 must be set to 0x6 in order to ensure correct operation.

So modified the SYNC2 value of OCP2SCP TIMING register to 0x6 in all the
platforms that use OCP2SCP driver except AM437x. Also introduced a new
compatible property since we don't want to modify the OCP2SCP TIMING
register for AM437x.

The sections in TRM where the above caution can be found is mentioned below.
AM572x TRM SPRUHZ6 (http://www.ti.com/lit/ug/spruhz6/spruhz6.pdf) under
section 26.3.2.2, table 26-26.

OMAP4430 TRM SWPU231AP (http://www.ti.com/lit/ug/swpu231ap/swpu231ap.pdf)
under section 23.12.6.2.2 , Table 23-1213.

OMAP4460 TRM SWPU235AB (http://www.ti.com/lit/ug/swpu235ab/swpu235ab.pdf)
under section 23.12.6.2.2, Table 23-1213.

OMAP543x TRM SWPU249 (http://www.ti.com/lit/pdf/swpu249)
under section 27.3.2.2, Table 27-27.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Praneeth Bajjuri <praneeth@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>