ARM: option for loading modules into vmalloc area

Usually modules are loaded into small area prior to the kernel
text because they are linked with the kernel using short calls.
Compile-time instrumentation like GCOV or KASAN bloats code a lot,
and as a result huge modules no longer fit into reserved area.

This patch adds option CONFIG_MODULES_USE_VMALLOC which lifts
limitation on amount of loaded modules. It links modules using
long-calls (option -mlong-calls) and loads them into vmalloc area.

In few places exported symbols are called from inline assembly.
This patch adds macro for such call sites: __asmbl and __asmbl_clobber.
Call turns into single 'bl' or sequence 'movw; movt; blx' depending on
context and state of config option.

Unfortunately this option isn't compatible with CONFIG_FUNCTION_TRACER.
Compiler emits short calls to profiling function despite of -mlong-calls.
This is a bug in GCC, but ftrace anyway needs an update to handle this.

Signed-off-by: Konstantin Khlebnikov <k.khlebnikov@samsung.com>
Patch-mainline: linux-arm-kernel @ 18/11/2014, 20:21:46
Change-Id: Iea7990a033c060c26f5782125fb63d6f96a9d218
Signed-off-by: Shubham Aggarwal <shubagga@codeaurora.org>