iris: Remove unneccessary sc null check
What does this MR do and why?
iris: Remove unneccessary sc null check
After 1da1bcd0383, sc has already been dereferenced on all paths at this
sc null check.
Fix defect reported by Coverity Scan.
Dereference before null check (REVERSE_INULL)
check_after_deref: Null-checking sc suggests that it may be null, but it
has already been dereferenced on all paths leading to the check.
Fixes: 1da1bcd0383 ("iris: pull WA 22014412737 into emit_3dprimitive_was")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>