kselftest/arm64: hwcap: fix f8dp2 cpuinfo name

The F8DP2 DPISA extension has a separate cpuinfo field, named
accordingly.
Change the erroneously placed name of "f8dp4" to "f8dp2".

Fixes: 44d10c27 ("kselftest/arm64: Add 2023 DPISA hwcap test coverage")
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240816153251.2833702-3-andre.przywara@arm.com


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>