kasan: Fix required compiler version

The first working GCC version to satisfy
CC_HAS_WORKING_NOSANITIZE_ADDRESS is GCC 8.3.0.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89124


Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200623112448.GA208112@elver.google.com