Revert "common: add discard threads option, descriptions and flags"

This reverts commit 1239568e18.
The commit was merged prematurely without testing.

Signed-off-by: Srinivasa Bharath Kanta <skanta@redhat.com>

src/common/options/global.yaml.in

@@ -4015,39 +4015,15 @@ options:
   default: false
   with_legacy: true
 - name: bdev_enable_discard
-  desc: send discards to the block device
   type: bool
   level: advanced
   default: false
   with_legacy: true
-  flags:
-  - runtime
-  see_also:
-  - bdev_async_discard
-  - bdev_async_discard_threads
 - name: bdev_async_discard
-  desc: send discards to the block device in one or more threads
-  type: uint
+  type: bool
   level: advanced
   default: false
-  with_legacy: false
-  flags:
-  - runtime
-  see_also:
-  - bdev_enable_discard
-  - bdev_async_discard_threads
-- name: bdev_async_discard_threads
-  desc: number of discard threads used to issue discards to the device
-  type: uint
-  level: advanced
-  default: 1
-  min: 1
-  with_legacy: false
-  flags:
-  - runtime
-  see_also:
-  - bdev_enable_discard
-  - bdev_async_discard
+  with_legacy: true
 - name: bdev_flock_retry_interval
   type: float
   level: advanced