The entire memory range under 1M is unconditionally reserved in
setup_arch(), so there is no need for crash_reserve_low_1M() anymore.

Remove this function.
Signed-off-by: NMike Rapoport <rppt@linux.ibm.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210601075354.5149-4-rppt@kernel.org