Fix output argument type for convolutions

Was out_t, which wasn't in the data types table.
Switch to acc_t, the size of the accumulator, which
is the output type for the convolutions.

Also added some types into the pseudocode to clarify
what types variables are.

Signed-off-by: Eric Kunze <eric.kunze@arm.com>
Change-Id: I210220199c2d39b16938094022339286df040545