usb: xhci: add USB Port Register Set struct

usb: xhci: add USB Port Register Set struct

Introduce a new struct for the Host Controller USB Port Register Set to
enhance readability and maintainability.

The Host Controller Operational Registers (struct 'xhci_op_regs') span from
offset 0x0 to 0x3FF and consist of fixed fields. Following these fixed
fields are the Host Controller USB Port Register Sets, which are dynamic
and repeat from 1 to MaxPorts, as defined by HCSPARAMS1.

Currently, the struct 'xhci_op_regs' includes:
 __le32 port_status_base;		The first PORTSC
 __le32 port_power_base;		The first PORTPMSC
 __le32 port_link_base;			The first PORTLI
 __le32 reserved5;			The first PORTHLPMC, not reserved
 __le32 reserved6[NUM_PORT_REGS*254];	Port registers 2 to MaxPorts

Replace this with the simpler:
 struct xhci_port_regs port_regs[];	Port registers 1 to MaxPorts

Host Controller USB Port Register Set:
| Offset	| Mnemonic	| Register Name
--------------------------------------------------------------------------
| 0x0		| PORTSC	| Port Status and Control
| 0x4		| PORTPMSC	| Port Power Management Status and Control
| 0x8		| PORTLI	| Port Link Info
| 0xC		| PORTHLPMC	| Port Hardware LPM Control

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://patch.msgid.link/20251119142417.2820519-8-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>