Cleanup: Suppress Coverity dereference before/after NULL check reports

f224eddf922a33ca4b86d83148e9e6fa155fc290 began dereferencing a NULL
checked pointer in zpl_vap_init(), which made Coverity complain because
either the dereference is unsafe or the NULL check is unnecessary. Upon
inspection, this pointer is guaranteed to never be NULL because it is
from the Linux kernel VFS. The calls into ZFS simply would not make
sense if this pointer were NULL, so the NULL check is unnecessary.

Reported-by: Coverity (CID 1527260)
Reported-by: Coverity (CID 1527262)
Reviewed-by: Mariusz Zaborski <mariusz.zaborski@klarasystems.com>
Reviewed-by: Youzhong Yang <yyang@mathworks.com>
Signed-off-by: Richard Yao <richard.yao@alumni.stonybrook.edu>
Closes #14170