UBUNTU: [Config] update configs and annotations after rebase to 5.11-rc3

UBUNTU: [Config] update configs and annotations after rebase to 5.11-rc3

 - Introduce CONFIG_NULL_TTY, enabling it as a module everywhere except
   on s390x.

 - ENABLE_MUST_CHECK has been removed by 196793946264 ("Compiler
   Attributes: remove CONFIG_ENABLE_MUST_CHECK"), so let's also remove
   it from the annotations file.

 - Drop CONFIG_KVM_ARM_PMU from annotations file: 8cbebc4118b5 ("KVM:
   arm64: Replace KVM_ARM_PMU with HW_PERF_EVENTS")

 - Drop CONFIG_USB_FSL_USB2 from annotations file: a390bef7db1f ("usb:
   gadget: fsl_mxc_udc: Remove the driver")

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>