ARM: davinci: streamline sysmod access

There are instances of IO_ADDRESS() being used for system module
(sysmod) register access. Eliminate this in favor of a ioremap()
based access. ioremap() the entire sysmod address space once during
boot-up and provide a helper macro to access specific register
offsets within the address space.

With this, also eliminate ioremap() of specific sysmodule registers
related to VPIF happening in DM646x EVM code.

While at it, also eliminate some duplicate sysmod register offset macros
defined in code and place offset definitions at one place in davinci.h

Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
[nsekhar@ti.com: removed the addition of ifndef __ASSEMBLER__
in davinci.h, eliminate IO_ADDRESS() usage left out in dm646x.c,
cleanup VPIF sysmodule register access as part of this patch and
keep all sysmod offsets in davinci.h Also, convert the WARN_ON()
on failure to setup sysmod base to BUG_ON()]
Signed-off-by: Sekhar Nori <nsekhar@ti.com>