MIPS: module: fix incorrect IS_ERR_VALUE macro usages

MIPS: module: fix incorrect IS_ERR_VALUE macro usages

IS_ERR_VALUE macro should be used only with unsigned long type.
Specifically it works incorrectly with longer types.

The patch follows conclusion from discussion on LKML [1][2].

[1]: http://permalink.gmane.org/gmane.linux.kernel/2120927
[2]: http://permalink.gmane.org/gmane.linux.kernel/2150581

[ralf@linux-mips.org: While it may not immediately be obvious, the type
of st_value in the end is an unsigned long equivalent so the invocation
of IS_ERR_VALUE() was valid but I'm applying the patch anyway for
clarity.]

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/12553/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>