arm64: Add part number for Arm Cortex-A78AE

arm64: Add part number for Arm Cortex-A78AE

Add the MIDR part number info for the Arm Cortex-A78AE[1] and add it to
spectre-BHB affected list[2].

[1]: https://developer.arm.com/Processors/Cortex-A78AE
[2]: https://developer.arm.com/Arm%20Security%20Center/Spectre-BHB

Cc: Catalin Marinas <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: James Morse <[email protected]>
Signed-off-by: Chanho Park <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>