On the v850, the elf toolchain uses a `_' prefix for all user symbols
(I'm not sure why, since most toolchains seem to have dropped this sort
of thing).

The attached patch adds the ability to deal with this, if the macro
MODULE_SYMBOL_PREFIX is defined by <asm/module.h>.  This only affects
places where symbol names come from the user, e.g., EXPORT_SYMBOL, or
the explicit symbol-names used in kernel/module.c itself.

[Tweaked a little by Rusty, original by Miles Bader]