arm: v7R: Add initial support

The Cortex-R* processors are a mid-range CPUs for use in deeply-embedded,
real-time systems. It implements the ARMv7-R architecture, and includes
Thumb-2 technology for optimum code density and processing throughput.

Except for MPU(Memory Protection Unit) and few CP15 registers, most of the
features are compatible with v7 architecture. So,reuse the same armv7
folder and introduce a new config CPU_V7R in order to differentiate
from v7 based platforms.

Tested-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>