x86: simplify set_bitmap in ioport_32.c

Simplify set_bitmap(). This is not in a hotpath and we really can use the
straight forward loop through those bits. A similar implementation is used
in the 64 bit code as well.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>