linux-yocto/6.10: cfg: arm64 configuration updates

Integrating the following commit(s) to linux-yocto/.:

1/2 [
    Author: Ross Burton
    Email: ross.burton@arm.com
    Subject: features/security: fix Meltdown/Spectre configurations
    Date: Thu, 12 Sep 2024 16:42:50 +0100

    These are both specific to x86 so move them into the x86 file, and were
    renamed to have a MITIGATION_ prefix in 6.9.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

2/2 [
    Author: Ross Burton
    Email: ross.burton@arm.com
    Subject: bsp/genericarm64: update for 6.10 kconfig symbol renames
    Date: Thu, 12 Sep 2024 16:42:51 +0100

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
]

Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>