usb: xhci: rename 'irq_pending' to 'iman'

usb: xhci: rename 'irq_pending' to 'iman'

The Interrupt Register Set contains Interrupt Management register (IMAN).
The IMAN register contains the following fields:
 - Bit 0:	Interrupt Pending (IP)
 - Bit 1:	Interrupt Enable (IE)
 - Bits 31:2:	RsvdP (Reserved and Preserved)

Tn the xhci driver, the pointer currently named 'irq_pending' refers to the
IMAN register. However, the name "irq_pending" only describes one of the
fields within the IMAN register, rather than the entire register itself.
To improve clarity and better align with the xHCI specification,
the pointer is renamed to 'iman'.

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/20250515135621.335595-22-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>