arm64: vdso*: place got/plt sections in .rodata

The vDSO will not contain absolute relocations, so place these
sections in .rodata.

Signed-off-by: Joey Gouly <joey.gouly@arm.com>
Link: https://lore.kernel.org/linux-arm-kernel/00abb0c5-6360-0004-353f-e7a88b3bd22c@arm.com/
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Link: https://lore.kernel.org/r/20220628151307.35561-3-joey.gouly@arm.com


Signed-off-by: Will Deacon <will@kernel.org>