[ARM] 4074/1: Flat loader stack alignment

The ARM EABI requires doubleword (8-byte) stack alignment at all public entry
points.  The patch below makes the bFLT loader honour this.
It's always safe to start with a doubleword aligned stack so it doesn't seem
worth making this conditional on CONFIG_AEABI.

Paul

Signed-off-by: Paul Brook <paul@codesourcery.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>