fix broken kdump_get_arch_recommend_size
    
    Resolves: bz2045971
    Upstream: Fedora
    Conflict: None
    
    commit 2df55984f66bc2a67c881eab0e33139d2ddc0461
    Author: Coiby Xu <coxu@redhat.com>
    Date:   Wed Jan 26 08:48:18 2022 +0800
    
        fix broken kdump_get_arch_recommend_size
    
        shellcheck finds the following problem,
        $ shellcheck kdump-lib.sh
        In kdump-lib.sh line 876:
                get_recommend_size "$sys_mem" "$ck_cmdline"
                                               ^---------^ SC2154: ck_cmdline is referenced but not assigned (did you mean '_ck_cmdline'?).
    
        s/ck_cmdline/_ck_cmdline to fix kdump_get_arch_recommend_size.
    
        Note s/sys_mem/_sys_mem as well to make the changes consistent.
    
        Fixes: 105c016 ("factor out kdump_get_arch_recommend_crashkernel")
        Signed-off-by: Coiby Xu <coxu@redhat.com>
        Acked-by: Tao Liu <ltao@redhat.com>
    
    Signed-off-by: Coiby Xu <coxu@redhat.com>