arm64: Show three registers per line

Displaying two registers per line takes 15 lines.  That improves to just
10 lines if we display three registers per line, which reduces the amount
of information lost when oopses are cut off.  It stays within 80 columns
and matches x86-64.
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210420172245.3679077-1-willy@infradead.orgSigned-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kernel/process.c

@@ -292,13 +292,10 @@ void __show_regs(struct pt_regs *regs)
 	i = top_reg;
 
 	while (i >= 0) {
-		printk("x%-2d: %016llx ", i, regs->regs[i]);
-		i--;
+		printk("x%-2d: %016llx", i, regs->regs[i]);
 
-		if (i % 2 == 0) {
-			pr_cont("x%-2d: %016llx ", i, regs->regs[i]);
-			i--;
-		}
+		while (i-- % 3)
+			pr_cont(" x%-2d: %016llx", i, regs->regs[i]);
 
 		pr_cont("\n");
 	}