phy: mediatek: allow compile-testing the hdmi phy

Compile-testing the DRM_MEDIATEK_HDMI driver shows two missing
dependencies, one results in a link failure:

arm-linux-gnueabi-ld: drivers/phy/mediatek/phy-mtk-hdmi.o: in function `mtk_hdmi_phy_probe':
phy-mtk-hdmi.c:(.text+0xd8): undefined reference to `__clk_get_name'
arm-linux-gnueabi-ld: phy-mtk-hdmi.c:(.text+0x12c): undefined reference to `devm_clk_register'
arm-linux-gnueabi-ld: phy-mtk-hdmi.c:(.text+0x250): undefined reference to `of_clk_add_provider'
arm-linux-gnueabi-ld: phy-mtk-hdmi.c:(.text+0x298): undefined reference to `of_clk_src_simple_get'

The other one is a harmless warning:

WARNING: unmet direct dependencies detected for PHY_MTK_HDMI
  Depends on [n]: ARCH_MEDIATEK [=n] && OF [=y]
  Selected by [y]:
  - DRM_MEDIATEK_HDMI [=y] && HAS_IOMEM [=y] && DRM_MEDIATEK [=y]

Fix these by adding dependencies on CONFIG_OF and CONFIG_COMMON_CLK.
With that done, there is also no reason against adding
CONFIG_COMPILE_TEST.

Fixes: b28be59a2e ("phy: mediatek: Move mtk_hdmi_phy driver into drivers/phy/mediatek folder")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20201204135650.2744481-1-arnd@kernel.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/mediatek/Kconfig

@@ -40,7 +40,9 @@ config PHY_MTK_XSPHY
 
 config PHY_MTK_HDMI
 	tristate "MediaTek HDMI-PHY Driver"
-	depends on ARCH_MEDIATEK && OF
+	depends on ARCH_MEDIATEK || COMPILE_TEST
+	depends on COMMON_CLK
+	depends on OF
 	select GENERIC_PHY
 	help
 	  Support HDMI PHY for Mediatek SoCs.