x86: initialize io_bitmap_base on 32bit

commit db949bba3c (x86-32: use non-lazy
io bitmap context switching) broke ioperm for 32bit because it removed
the lazy initialization of io_bitmap_base and did not set it to the
real bitmap offset.

[ Impact: fix non-working sys_ioperm() on 32-bit kernels ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/cpu/common.c

@@ -1203,6 +1203,8 @@ void __cpuinit cpu_init(void)
 	load_TR_desc();
 	load_LDT(&init_mm.context);
 
+	t->x86_tss.io_bitmap_base = offsetof(struct tss_struct, io_bitmap);
+
 #ifdef CONFIG_DOUBLEFAULT
 	/* Set up doublefault TSS pointer in the GDT */
 	__set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);