kasan: inline random_tag for HW_TAGS

Using random_tag() currently results in a function call. Move its
definition to mm/kasan/kasan.h and turn it into a static inline function
for hardware tag-based mode to avoid uneeded function call.

Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://linux-review.googlesource.com/id/Iac5b2faf9a912900e16cca6834d621f5d4abf427