glibc: malloc: Add missing arena lock in malloc_info

glibc: malloc: Add missing arena lock in malloc_info

There are the multiple process crashes seen while using malloc_info.
Obtain the size information while the arena lock is acquired, and only
print it later.

Backport patch from https://sourceware.org/git/gitweb.cgi?p=glibc.git;
h=7a9368a1174cb15b9f1d6342e0e10dd90dae238d

(From OE-Core rev: 7ecbb31fbaf1d056c9301166700e2967bd623489)

Signed-off-by: Zhixiong Chi <zhixiong.chi@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>