realtek: rtl931x: fix missing CONFIG_COMMON_CLK_REALTEK config flag

When the realtek clock driver was introduced, CONFIG_COMMON_CLK_REALTEK
was not correctly disabled for other subtarget. Add the missing config
flag to fix compilation error on buildbot.

Fixes: 4850bd887c3a ("realtek: add RTL83XX clock driver")
Signed-off-by: Christian Marangi <[email protected]>

target/linux/realtek/rtl931x/config-5.10

@@ -12,6 +12,7 @@ CONFIG_CLKSRC_MMIO=y
 CONFIG_CLONE_BACKWARDS=y
 CONFIG_COMMON_CLK=y
 CONFIG_COMMON_CLK_BOSTON=y
+# CONFIG_COMMON_CLK_REALTEK is not set
 CONFIG_COMPAT_32BIT_TIME=y
 CONFIG_CONSOLE_LOGLEVEL_DEFAULT=15
 CONFIG_CPU_BIG_ENDIAN=y