ARM: SPEAr3xx: Add device-tree support to SPEAr3xx architecture

ARM: SPEAr3xx: Add device-tree support to SPEAr3xx architecture

This patch adds a generic target for SPEAr3xx machines that can be configured
via the device-tree. Currently the following devices are supported via the
devicetree:

- VIC interrupts
- PL011 UART
- PL061 GPIO
- PL110 CLCD
- SP805 WDT
- Synopsys DW I2C
- Synopsys DW ethernet
- ST FSMC-NAND
- ST SPEAR-SMI
- ST SPEAR-KEYBOARD
- ST SPEAR-RTC
- ARASAN SDHCI-SPEAR
- SPEAR-EHCI
- SPEAR-OHCI

Other peripheral devices will follow in later patches.

This also removes IO_ADDRESS macro and creates 16 MB static mappings instead of
4K for individual peripherals. This is done to have efficient TLB lookup for any
I/O windows that are located closely together. ioremap() on this range will
return this mapping only instead of creating another.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>