target/arm: Adjust interface of sve_ld1_host_fn

target/arm: Adjust interface of sve_ld1_host_fn

The current interface includes a loop; change it to load a
single element.  We will then be able to use the function
for ld{2,3,4} where individual vector elements are not adjacent.

Replace each call with the simplest possible loop over active
elements.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200508154359.7494-11-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>