module/decompress: generate sysfs string at compile time

compression_show() before (with noinline):
   0xffffffff810b5ff0 <+0>:     mov    %rdx,%rdi
   0xffffffff810b5ff3 <+3>:     mov    $0xffffffff81b55629,%rsi
   0xffffffff810b5ffa <+10>:    mov    $0xffffffff81b0cde2,%rdx
   0xffffffff810b6001 <+17>:    call   0xffffffff811b8fd0 <sysfs_emit>
   0xffffffff810b6006 <+22>:    cltq
   0xffffffff810b6008 <+24>:    ret

After:
   0xffffffff810b5ff0 <+0>:     mov    $0xffffffff81b0cde2,%rsi
   0xffffffff810b5ff7 <+7>:     mov    %rdx,%rdi
   0xffffffff810b5ffa <+10>:    call   0xffffffff811b8fd0 <sysfs_emit>
   0xffffffff810b5fff <+15>:    cltq
   0xffffffff810b6001 <+17>:    ret

Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Aaron Tomlin <atomlin@redhat.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>