ARM: OMAP2+: am33xx: Add AM335XEVM machine support

This patch adds minimal support for AM335X machine init.

During last merge window, two separate patches supporting am33xx
machine init had been submitted,

1. Link to earlier Baseport patch submission (Legacy):
http://www.mail-archive.com/linux-omap@vger.kernel.org/msg59325.html
2. Link to earlier DT based machine init support patch submission:
http://www.mail-archive.com/linux-omap@vger.kernel.org/msg61398.html



And both had got accepted at that time, but got missed during
merge window.

But now, since we have taken decision to make am33xx as a separate
class and not to follow omap3 family, these patches needs to changes
accordingly (only changes),

 - Combine both the patches, since early init and timer init
   used in board-generic.c file requires them.
 - Remove dependency on AM3517EVM, and only use DT approach
   for machine init.
 - Change the config option (as changed recently)
   CONFIG_SOC_OMAPAM33XX --> CONFIG_SOC_AM33XX

Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>