modpost: Fix section warnings for ARM for many compilers

It turns out that many compilers don't show section warnings on ARM
currently because handling for ARM_CALL relocs are missing from
modpost.c.

Based on commit c2e26114 ([ARM] 3205/1: Handle new EABI relocations when
loading kernel modules) it seems that R_ARM_PC24, R_ARM_CALL and
R_ARM_JUMP24 can be handled the same way.

Note that at least Debian libc6-dev is missing defines for both
R_ARM_CALL and R_ARM_JUMP24 in /usr/include/elf.h. So for now
we need to define them in modpost.c if not defined.

Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Anders Kaseorg <andersk@ksplice.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>