They are currently emitted identically to an explicit zero row, which is
wrong - a zero row would not be masked as it contains an operation (setting
the component to zero *is* an explicit operation; only leaving it untouched
is an implicit noop).
And also emit a 1 coefficient in the expected location in the data matrix.
I have verified that the resulting x86 and NEON kernels are bit-identical.
Signed-off-by: Niklas Haas <git@haasn.dev>