powerpc/powermac: Use early_* IO variants in via_calibrate_decr()

On a powermac platform, via the call path:

  start_kernel()
    time_init()
      ppc_md.calibrate_decr() (pmac_calibrate_decr)
        via_calibrate_decr()

ioremap() and iounmap() are called. The unmap can enable interrupts
unexpectedly (cond_resched() in vunmap_pmd_range()), which causes a
warning later in the boot sequence in start_kernel().

Use the early_* variants of these IO functions to prevent this.

The issue is pre-existing, but is surfaced by commit 721255b9
("genirq: Use a maple tree for interrupt descriptor management").
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230706010816.72682-1-bgray@linux.ibm.com

arch/powerpc/platforms/powermac/time.c

@@ -26,8 +26,8 @@
 #include <linux/rtc.h>
 #include <linux/of_address.h>
 
+#include <asm/early_ioremap.h>
 #include <asm/sections.h>
-#include <asm/io.h>
 #include <asm/machdep.h>
 #include <asm/time.h>
 #include <asm/nvram.h>
@@ -182,7 +182,7 @@ static int __init via_calibrate_decr(void)
 		return 0;
 	}
 	of_node_put(vias);
-	via = ioremap(rsrc.start, resource_size(&rsrc));
+	via = early_ioremap(rsrc.start, resource_size(&rsrc));
 	if (via == NULL) {
 		printk(KERN_ERR "Failed to map VIA for timer calibration !\n");
 		return 0;
@@ -207,7 +207,7 @@ static int __init via_calibrate_decr(void)
 
 	ppc_tb_freq = (dstart - dend) * 100 / 6;
 
-	iounmap(via);
+	early_iounmap((void *)via, resource_size(&rsrc));
 
 	return 1;
 }