Fix compilation warning: incorrect format specifier for type 'ssize_t'.

warning: format '%ld' expects argument of type 'long int',
but argument 7 has type 'ssize_t {aka int}' [-Wformat]

Change-Id: I823835a26320a3abb82f8dff9fbe82e5132e7556
Signed-off-by: Scott Fan <fancp2007@gmail.com>