greybus: es2.c: Declare local __le64 not u64

The value passed to le64_to_cpu wants to be an __le64 not a u64.
Note to self - remember to run "make check"

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reported-by: Greg Kroah-Hartman <gregkh@google.com>
Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>