net: usb: asix: ax88772: Increase phy_name size

net: usb: asix: ax88772: Increase phy_name size

GCC compiler (Debian 14.2.0-17) is not happy about printing
into a too short buffer (when build with `make W=1`):

 drivers/net/usb/ax88172a.c:311:9: note: ‘snprintf’ output between 4 and 66 bytes into a destination of size 20

Indeed, the buffer size is chosen based on some assumptions,
while in general the assigned name might not fit. Increase
the buffer size to cover the minimum required one. With that,
change snprintf() to use sizeof() instead of the hard coded
value.

While at it, make sure that the PHY address is not bigger than
the allowed maximum.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20250324144751.1271761-3-andriy.shevchenko@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>