ARM: arm_cpu_reset: make it possible to use high vectors for reset_exc

ARM: arm_cpu_reset: make it possible to use high vectors for reset_exc

If hivecs are being used on reset, the CPU should come out of reset at
the hivecs reset vector (0xFFFF0000)

Signed-off-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: 3afc69c4f58f60aa2bbee7b91574a4eb414b1c23.1387160489.git.peter.crosthwaite@xilinx.com
[ PC Changes:
 * Fixed Grammar error in commit message
 * Elaborated commit message.
]
Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>