x86/EISA: Dereference memory directly instead of using readl()

Sparse expect an __iomem pointer, but after converting the EISA probe to
memremap() the pointer is a regular memory pointer. Access it directly
instead.

[ tglx: Converted it to fix the already applied version  ]

Fixes: 80a4da05 ("x86/EISA: Use memremap() to probe for the EISA BIOS signature")
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/alpine.DEB.2.21.2408261015270.30766@angie.orcam.me.uk

arch/x86/kernel/eisa.c

@@ -11,13 +11,13 @@
 
 static __init int eisa_bus_probe(void)
 {
-	void *p;
+	u32 *p;
 
 	if ((xen_pv_domain() && !xen_initial_domain()) || cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
 		return 0;
 
 	p = memremap(0x0FFFD9, 4, MEMREMAP_WB);
-	if (p && readl(p) == 'E' + ('I' << 8) + ('S' << 16) + ('A' << 24))
+	if (p && *p == 'E' + ('I' << 8) + ('S' << 16) + ('A' << 24))
 		EISA_bus = 1;
 	memunmap(p);
 	return 0;