kexec: add KEXEC_FILE_NO_CMA as a legal flag

Commit 07d24902977e ("kexec: enable CMA based contiguous allocation")
introduces logic to use CMA-based allocation in kexec by default. As part
of the changes, it introduces a kexec_file_load flag to disable the use of
CMA allocations from userspace. However, this flag is broken since it is
missing from the list of legal flags for kexec_file_load. kexec_file_load
returns EINVAL when attempting to use the flag.

Fix this by adding the KEXEC_FILE_NO_CMA flag to the list of legal flags
for kexec_file_load.

Without this fix, kexec_file_load syscall will failed and return
'-EINVAL' when KEXEC_FILE_NO_CMA is specified.

Link: https://lkml.kernel.org/r/20250805211527.122367-2-makb@juniper.net
Fixes: 07d24902977e ("kexec: enable CMA based contiguous allocation")
Signed-off-by: Brian Mak <makb@juniper.net>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Young <dyoung@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Saravana Kannan <saravanak@google.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>