module/*.ko: prune .data, global .rodata

Evaluated every variable that lives in .data (and globals in .rodata)
in the kernel modules, and constified/eliminated/localised them
appropriately. This means that all read-only data is now actually
read-only data, and, if possible, at file scope. A lot of previously-
global-symbols became inlinable (and inlined!) constants. Probably
not in a big Wowee Performance Moment, but hey.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #12899

module/zfs/vdev_removal.c

@@ -94,7 +94,7 @@ typedef struct vdev_copy_arg {
  * doing a device removal.  This determines how much i/o we can have
  * in flight concurrently.
  */
-int zfs_remove_max_copy_bytes = 64 * 1024 * 1024;
+static const int zfs_remove_max_copy_bytes = 64 * 1024 * 1024;
 
 /*
  * The largest contiguous segment that we will attempt to allocate when
@@ -112,7 +112,7 @@ int zfs_remove_max_segment = SPA_MAXBLOCKSIZE;
  * not be cancelled.  This can result in a normally recoverable block
  * becoming permanently damaged and is not recommended.
  */
-int zfs_removal_ignore_errors = 0;
+static int zfs_removal_ignore_errors = 0;
 
 /*
  * Allow a remap segment to span free chunks of at most this size. The main