Software tag-based KASAN mode is fully initialized with kasan_init_tags(),
while the generic mode only requires kasan_init(). Move the
initialization message for tag-based mode into kasan_init_tags().

Also fix pr_fmt() usage for KASAN code: generic.c doesn't need it as it
doesn't use any printing functions; tag-based mode should use "kasan:"
instead of KBUILD_MODNAME (which stands for file name).

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
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Change-Id: Iddca9764b30ff0fab1922f26ca9d4f39b6f22673