CVE-2026-53200

In the Linux kernel, the following vulnerability has been resolved:

KVM: arm64: nv: Fix handling of XN[0] when !FEAT_XNX

XN has already been extracted from its bitfield position so using
FIELD_PREP() on the mask that clears XN[0] is completely broken, having
the effect of unconditionally granting execute permissions...

Fix the obvious mistake by manipulating the right bit.