The current function that both allocates and adds the interrupter isn't
optimal when using several interrupters. The array of interrupters need
to be protected with a lock while adding or removing interrupters.
If memory is allocated under the default xhci spinlock then GFP_KERNEL
can't be used.

There is no need to allocate the interrupter memory under the lock, so
split this code into separate unlocked allocate part, and a lock
protected add part.
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Message-ID: <20230602144009.1225632-6-mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>