drivers: remove uninit_hardware() from misc/kdl and misc/test

GCC complained of missing prototype for "uninit_hardware()" and,
as -Werror is enabled for these targets, build was broken for them.

While src/system/kernel/device_manager/legacy_drivers.cpp supports
that hook in legacy drivers binaries:

- no header mentions it.
- these two were the only places in-tree that implemented that hook.
- both were basically no-ops.

Change-Id: Ifb08846351b92a2d0fbbe95db2eee0e424ae5997
Reviewed-on: https://review.haiku-os.org/c/haiku/+/6180
Tested-by: Automation <automation@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

src/add-ons/kernel/drivers/misc/kdl.c

@@ -37,14 +37,6 @@ init_hardware(void)
 }
 
 
-status_t
-uninit_hardware(void)
-{
-	dprintf("kdl: uninit_hardware\n");
-	return B_OK;
-}
-
-
 status_t
 init_driver(void)
 {

src/add-ons/kernel/drivers/misc/test.c

@@ -37,14 +37,6 @@ init_hardware(void)
 }
 
 
-status_t
-uninit_hardware(void)
-{
-	dprintf("test: uninit_hardware\n");
-	return B_OK;
-}
-
-
 status_t
 init_driver(void)
 {