net: ethernet: mediatek: Fix overlapping capability bits.

Both MTK_TRGMII_MT7621_CLK and MTK_PATH_BIT are defined as bit 10.

This can causes issues on non-MT7621 devices which has the
MTK_PATH_BIT(MTK_ETH_PATH_GMAC1_RGMII) and MTK_TRGMII capability set.
The wrong TRGMII setup code can be executed. The current wrongly executed
code doesn’t do any harm on MT7623 and the TRGMII setup for the MT7623
SOC side is done in MT7530 driver So it wasn’t noticed in the test.

Move all capability bits in one enum so that they are all unique and easy
to expand in the future.

Because mtk_eth_path enum is merged in to mkt_eth_capabilities, the
variable path value is no longer between 0 to number of paths,
mtk_eth_path_name can’t be used anymore in this form. Convert the
mtk_eth_path_name array to a function to lookup the pathname.

The old code walked thru the mtk_eth_path enum, which is also merged
with mkt_eth_capabilities. Expand array mtk_eth_muxc so it can store the
name and capability bit of the mux. Convert the code so it can walk thru
the mtk_eth_muxc array.

Fixes: 8efaa653

 ("net: ethernet: mediatek: Add MT7621 TRGMII mode support")
Signed-off-by: René van Dorst <opensource@vdorst.com>

v1->v2:
- Move all capability bits in one enum, suggested by Willem de Bruijn
- Convert the mtk_eth_path_name array to a function to lookup the pathname
- Expand array mtk_eth_muxc so it can also store the name and capability
  bit of the mux
- Updated commit message

Signed-off-by: David S. Miller <davem@davemloft.net>