usb: xhci: remove error handling from xhci_add_interrupter()

usb: xhci: remove error handling from xhci_add_interrupter()

Remove redundant error handling from xhci_add_interrupter() instead of
trying to accommodate them in future changes.

======== Reasoning for the removal ========

Function xhci_add_interrupter() is invoked in two scenarios:

Primary Interrupter Setup (ID 0):
 The maximum number of interrupters is always greater than zero, and the
 primary interrupter is always allocated as part of the driver's
 initialization process. In case of failure, the xHCI driver errors and
 exits.

Secondary Interrupter Creation (ID >= 1):
 The interrupter is pre-allocated, and an empty slot is identified before
 invoking xhci_add_interrupter().

In both cases, the existing error handling within xhci_add_interrupter() is
redundant and unnecessary.

Upcoming Changes:
 In the subsequent commit, interrupter initialization will move from
 xhci_mem_init() to xhci_init(). This change is necessary to facilitate
 the ability to restart the xHCI driver without re-allocating memory.
 As a result, the allocated interrupter must be stored in the interrupters
 pointer array before initialization.

 Consequently, xhci_create_secondary_interrupter() would need to handle
 pointer removal for allocated 'interrupters' array upon failure, although
 xhci_add_interrupter() will never fail.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250515135621.335595-11-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>