ACPI: asus_acpi: fix proc files parsing

ICC complains about a "Pointless comparsion of unsigned interger with zero"
@ line 760 & 808 of asus_acpi.c

parse_arg() mentioned below returns -E but it's copied into unsigned variable...

Signed-off-by: Darren Jenkins <darrenrjenkins@gmail.com>
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Len Brown <len.brown@intel.com>