ARM: Auto calculate ZRELADDR and provide option for exceptions

As long as the zImage is placed within the 128MB range from the start of
memory, ZRELADDR (Address where the decompressed kernel will be placed,
usually == PHYS_OFFSET + TEXT_OFFSET) can be determined at run-time by
masking PC with 0xf80000000.

Running through all the Makefile.boot, all those zreladdr-y
addresses == 0x[0-f][08]00_0000 + TEXT_OFFSET can be determined at
run-time.

Option CONFIG_AUTO_ZRELADDR and CONFIG_ZRELADDR are introduced,
CONFIG_ZRELADDR _must_ be explicitly specified if:

- ((zreladdr-y - TEXT_OFFSET) & ~0xf8000000) != 0, which means
  masking PC with 0xf8000000 will result in an incorrect address.
  Currently this is only a problem on u300.

- or the assumption of the zImage being loaded by the bootloader within
  the first 128MB of RAM is incorrect

- or when ZBOOT_ROM is used, where the above assumption is usually wrong.

[ukleinek: changed mask from 0xf0000000 to 0xf8000000 for mx1 and shark
+ some review fixes from the mailing list]

Original-Idea-and-Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
Signed-off-by: Eric Miao <eric.miao@canonical.com>
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>