arm64/vdso: don't leak kernel addresses

Since commit ad67b74d ("printk: hash addresses printed with %p"),
two obfuscated kernel pointer are printed at every boot:

    vdso: 2 pages (1 code @ (____ptrval____), 1 data @ (____ptrval____))

Remove the the print completely, as it's useless without the addresses.

Fixes: ad67b74d

 ("printk: hash addresses printed with %p")
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Matteo Croce <mcroce@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>