x86/boot/e820: Clean up __e820__range_add() a bit

 - Use 'idx' index variable instead of a weird 'x'
 - Make the error message E820-specific
 - Group the code a bit better

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Andy Shevchenko <andy@kernel.org>
Cc: Arnd Bergmann <arnd@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Juergen Gross <jgross@suse.com>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Woodhouse <dwmw@amazon.co.uk>
Link: https://patch.msgid.link/20250515120549.2820541-15-mingo@kernel.org

Author: ingomolnar

arch/x86/kernel/e820.c

@@ -166,17 +166,18 @@ int e820__get_entry_type(u64 start, u64 end)
  */
 static void __init __e820__range_add(struct e820_table *table, u64 start, u64 size, enum e820_type type)
 {
-	int x = table->nr_entries;
+	int idx = table->nr_entries;
 
-	if (x >= ARRAY_SIZE(table->entries)) {
-		pr_err("too many entries; ignoring [mem %#010llx-%#010llx]\n",
-		       start, start + size - 1);
+	if (idx >= ARRAY_SIZE(table->entries)) {
+		pr_err("too many E820 table entries; ignoring [mem %#010llx-%#010llx]\n",
+		       start, start + size-1);
 		return;
 	}
 
-	table->entries[x].addr = start;
-	table->entries[x].size = size;
-	table->entries[x].type = type;
+	table->entries[idx].addr = start;
+	table->entries[idx].size = size;
+	table->entries[idx].type = type;
+
 	table->nr_entries++;
 }