x86/arm64/kasan, mm: Fix kasan build

Fix build errors due to bad cherry-pick of upstream commit
69786cdb379b ("x86/kasan, mm: Introduce generic kasan_populate_zero_shadow()").

Fixes: LSK commit be8a0705 ("x86/kasan, mm: Introduce generic kasan_populate_zero_shadow()")
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>