usb: xhci: rename 'irq_control' to 'imod'

usb: xhci: rename 'irq_control' to 'imod'

The Interrupt Register Set contains Interrupt Moderation register (IMOD).
The IMOD register contains the following fields:
 - Bits 15:0:	Interrupt Moderation Interval (IMODI)
 - Bits 31:16:	Interrupt Moderation Counter (IMODC)

In the xHCI driver, the pointer currently named 'irq_control' refers to the
IMOD register. However, the name 'irq_control' does not accurately describe
the register or its contents, and the xHCI specification does not use the
term "irq control" or "interrupt control" for this register. To improve
clarity and better align with the xHCI specification, the pointer is
renamed to 'imod'.

Additionally, the IMOD register fields IMODI & IMODC have their own masks,
which are also renamed for consistency:
 * 'ER_IRQ_INTERVAL_MASK' -> 'IMODI_MASK'
 * 'ER_IRQ_COUNTER_MASK' -> 'IMODC_MASK'

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/20250515135621.335595-23-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>