phy: ralink: phy-mt7621-pci: drop 'of_match_ptr' to fix -Wunused-const-variable

phy: ralink: phy-mt7621-pci: drop 'of_match_ptr' to fix -Wunused-const-variable

The of_device_id is included unconditionally by of.h header and used
in the driver as well. Remove of_match_ptr to fix W=1 compile test
warning with !CONFIG_OF:

drivers/phy/ralink/phy-mt7621-pci.c:341:34: warning: unused variable 'mt7621_pci_phy_ids' [-Wunused-const-variable]

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Link: https://lore.kernel.org/r/20210603043219.32646-1-sergio.paracuellos@gmail.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>