broadcom/compiler: free defin and defout arrays if they already exist

broadcom/compiler: free defin and defout arrays if they already exist

Just like we do for everything else here, since we are going to realloc
them again right below. Notice this is not exactly a memory leak, since
all these arrays are allocated with ralloc using v3d_compile as context,
so all allocations will be eventually freed when the context is destroyed.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24001>