x86/boot: Move EISA setup to a separate file

EISA has absolutely nothing to do with traps, so move it out of traps.c
into its own eisa.c file.

Furthermore, the EISA bus detection does not need to run during
very early boot, it's good enough to run it before the EISA bus
and drivers are initialized.

I.e. instead of calling it from the very early trap_init() code,
make it a subsys_initcall().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20170828064956.515322409@linutronix.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/Makefile

@@ -111,6 +111,7 @@ obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= paravirt-spinlocks.o
 obj-$(CONFIG_PARAVIRT_CLOCK)	+= pvclock.o
 obj-$(CONFIG_X86_PMEM_LEGACY_DEVICE) += pmem.o
 
+obj-$(CONFIG_EISA)		+= eisa.o
 obj-$(CONFIG_PCSPKR_PLATFORM)	+= pcspeaker.o
 
 obj-$(CONFIG_X86_CHECK_BIOS_CORRUPTION) += check.o

arch/x86/kernel/eisa.c

@@ -0,0 +1,18 @@
+/*
+ * EISA specific code
+ *
+ * This file is licensed under the GPL V2
+ */
+#include <linux/ioport.h>
+#include <linux/eisa.h>
+
+static __init int eisa_bus_probe(void)
+{
+	void __iomem *p = ioremap(0x0FFFD9, 4);
+
+	if (readl(p) == 'E' + ('I'<<8) + ('S'<<16) + ('A'<<24))
+		EISA_bus = 1;
+	iounmap(p);
+	return 0;
+}
+subsys_initcall(eisa_bus_probe);

arch/x86/kernel/traps.c

@@ -38,11 +38,6 @@
 #include <linux/smp.h>
 #include <linux/io.h>
 
-#ifdef CONFIG_EISA
-#include <linux/ioport.h>
-#include <linux/eisa.h>
-#endif
-
 #if defined(CONFIG_EDAC)
 #include <linux/edac.h>
 #endif
@@ -969,14 +964,6 @@ void __init trap_init(void)
 {
 	int i;
 
-#ifdef CONFIG_EISA
-	void __iomem *p = early_ioremap(0x0FFFD9, 4);
-
-	if (readl(p) == 'E' + ('I'<<8) + ('S'<<16) + ('A'<<24))
-		EISA_bus = 1;
-	early_iounmap(p, 4);
-#endif
-
 	set_intr_gate(X86_TRAP_DE, divide_error);
 	set_intr_gate_ist(X86_TRAP_NMI, &nmi, NMI_STACK);
 	/* int4 can be called from all */