net/mlx5: Kconfig: convert imply usage to weak dependency

MLX5_CORE uses the 'imply' keyword to depend on VXLAN, PTP_1588_CLOCK,
MLXFW and PCI_HYPERV_INTERFACE.

This was useful to force vxlan, ptp, etc.. to be reachable to mlx5
regardless of their config states.

Due to the changes in the cited commit below, the semantics of 'imply'
was changed to not force any restriction on the implied config.

As a result of this change, the compilation of MLX5_CORE=y and VXLAN=m
would result in undefined references, as VXLAN now would stay as 'm'.

To fix this we change MLX5_CORE to have a weak dependency on
these modules/configs and make sure they are reachable, by adding:
depend on symbol || !symbol.

For example: VXLAN=m MLX5_CORE=y, this will force MLX5_CORE to m

Fixes: def2fbf ("kconfig: allow symbols implied by y to become m")
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Cc: Nicolas Pitre <nico@fluxnic.net>
Cc: Arnd Bergmann <arnd@arndb.de>
Reported-by: Randy Dunlap <rdunlap@infradead.org>

drivers/net/ethernet/mellanox/mlx5/core/Kconfig

@@ -7,10 +7,10 @@ config MLX5_CORE
 	tristate "Mellanox 5th generation network adapters (ConnectX series) core driver"
 	depends on PCI
 	select NET_DEVLINK
-	imply PTP_1588_CLOCK
-	imply VXLAN
-	imply MLXFW
-	imply PCI_HYPERV_INTERFACE
+	depends on VXLAN || !VXLAN
+	depends on MLXFW || !MLXFW
+	depends on PTP_1588_CLOCK || !PTP_1588_CLOCK
+	depends on PCI_HYPERV_INTERFACE || !PCI_HYPERV_INTERFACE
 	default n
 	---help---
 	  Core driver for low level functionality of the ConnectX-4 and