mei: fix krealloc() misuse in in mei_cl_irq_read_msg()

If krealloc() returns NULL, it doesn't free the original. So any code
of the form 'foo = krealloc(foo, ...);' is almost certainly a bug.

Introduced by commit fcb136e1(mei: fix
reading large reposnes)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>