arm64: restore bogomips information in /proc/cpuinfo

commit 92e788b7 upstream.

As previously reported, some userspace applications depend on bogomips
showed by /proc/cpuinfo. Although there is much less legacy impact on
aarch64 than arm, it does break libvirt.

This patch reverts commit 326b16db ("arm64: delay: don't bother
reporting bogomips in /proc/cpuinfo"), but with some tweak due to
context change and without the pr_info().

Fixes: 326b16db ("arm64: delay: don't bother reporting bogomips in /proc/cpuinfo")
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
[ kamal: backport to 3.19-stable: applies to setup.c; context ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

arch/arm64/kernel/setup.c

@@ -520,6 +520,9 @@ static int c_show(struct seq_file *m, void *v)
 #ifdef CONFIG_SMP
 		seq_printf(m, "processor\t: %d\n", i);
 #endif
+		seq_printf(m, "BogoMIPS\t: %lu.%02lu\n\n",
+			   loops_per_jiffy / (500000UL/HZ),
+			   loops_per_jiffy / (5000UL/HZ) % 100);
 
 		/*
 		 * Dump out the common processor features in a single line.