arm: fix __efi_runtime_rel_start/end definitions

__efi_runtime_rel_start/end are defined as c variables for arm7 only in
order to force the compiler emit relative references. However, defining
those within a section definition will do the same thing since [0].
On top of that the v8 linker scripts define it as a symbol.

So let's remove the special sections from the linker scripts, the
variable definitions from sections.c and define them as a symbols within
the correct section.

[0] binutils commit 6b3b0ab89663 ("Make linker assigned symbol dynamic only for shared object")

Suggested-by: Sam Edwards <CFSworks@gmail.com>
Reviewed-by: Sam Edwards <CFSworks@gmail.com>
Tested-by: Sam Edwards <CFSworks@gmail.com> # Binary output identical
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

include/asm-generic/sections.h

@@ -34,6 +34,8 @@ extern char __priv_data_start[], __priv_data_end[];
 /* Start and end of .ctors section - used for constructor calls. */
 extern char __ctors_start[], __ctors_end[];
 
+extern char __efi_runtime_rel_start[], __efi_runtime_rel_stop[];
+
 /* function descriptor handling (if any).  Override
  * in asm/sections.h */
 #ifndef dereference_function_descriptor