net: dsa: MxL862xx: don't force-enable MAXLINEAR_GPHY

The newly added dsa driver attempts to enable the corresponding PHY driver,
but that one has additional dependencies that may not be available:

WARNING: unmet direct dependencies detected for MAXLINEAR_GPHY
Depends on [m]: NETDEVICES [=y] && PHYLIB [=y] && (HWMON [=m] || HWMON [=m]=n [=n])
Selected by [y]:
- NET_DSA_MXL862 [=y] && NETDEVICES [=y] && NET_DSA [=y]
aarch64-linux-ld: drivers/net/phy/mxl-gpy.o: in function `gpy_probe':
mxl-gpy.c:(.text.gpy_probe+0x13c): undefined reference to `devm_hwmon_device_register_with_info'
aarch64-linux-ld: drivers/net/phy/mxl-gpy.o: in function `gpy_hwmon_read':
mxl-gpy.c:(.text.gpy_hwmon_read+0x48): undefined reference to `polynomial_calc'

There is actually no compile-time dependency, as DSA correctly uses the
PHY abstractions. Remove the 'select' statement to reduce the complexity.

Fixes: 23794bec1cb6 ("net: dsa: add basic initial driver for MxL862xx switches")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/20260216105522.2382373-1-arnd@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>