ARM: Add caller information to ioremap

This allows the procfs vmallocinfo file to show who created the ioremap
regions.  Note: __builtin_return_address(0) doesn't do what's expected
if its used in an inline function, so we leave __arm_ioremap callers
in such places alone.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>