soc: qcom: wcnss: simplify allocation of req

soc: qcom: wcnss: simplify allocation of req

Get rid of automatic kfree and move allocation down to where it's used.

Use kzalloc_flex as we're dealing with a flexible array member.

Use struct_size to avoid some pointer math.

Add __counted_by for extra runtime analysis. Move the counting variable
assignment to right after allocation as required by __counted_by.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Link: https://lore.kernel.org/r/20260327025534.7864-1-rosenp@gmail.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>