efi/x86: Replace #ifdefs with IS_ENABLED() checks

When possible, IS_ENABLED() conditionals are preferred over #ifdefs,
given that the latter hide the code from the compiler entirely, which
reduces build test coverage when the option is not enabled.

So replace an instance in the x86 efi startup code.
Signed-off-by: NArd Biesheuvel <ardb@kernel.org>

arch/x86/platform/efi/efi.c

@@ -214,16 +214,13 @@ int __init efi_memblock_x86_reserve_range(void)
 	if (efi_enabled(EFI_PARAVIRT))
 		return 0;
 
-#ifdef CONFIG_X86_32
-	/* Can't handle data above 4GB at this time */
-	if (e->efi_memmap_hi) {
+	/* Can't handle firmware tables above 4GB on i386 */
+	if (IS_ENABLED(CONFIG_X86_32) && e->efi_memmap_hi > 0) {
 		pr_err("Memory map is above 4GB, disabling EFI.\n");
 		return -EINVAL;
 	}
-	pmap =  e->efi_memmap;
-#else
-	pmap = (e->efi_memmap |	((__u64)e->efi_memmap_hi << 32));
-#endif
+	pmap = (phys_addr_t)(e->efi_memmap | ((u64)e->efi_memmap_hi << 32));
+
 	data.phys_map		= pmap;
 	data.size 		= e->efi_memmap_size;
 	data.desc_size		= e->efi_memdesc_size;