x86/unwind/orc: Remove redundant initialization of 'mid' pointer in __orc_find()

The 'mid' pointer is being initialized with a value that is never read,
it is being re-assigned and used inside a for-loop. Remove the
redundant initialization.

Cleans up clang scan build warning:

  arch/x86/kernel/unwind_orc.c:88:7: warning: Value stored to 'mid' during its initialization is never read [deadcode.DeadStores]

Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20230920114141.118919-1-colin.i.king@gmail.com