scripts/gdb: fix invocation when CONFIG_COMMON_CLK is not set

CLK_GET_RATE_NOCACHE depends on CONFIG_COMMON_CLK.  Importing constants.py
when CONFIG_COMMON_CLK is not defined causes:

  (gdb) lx-symbols
  (...)
    File "scripts/gdb/linux/proc.py", line 15, in <module>
      from linux import constants
    File "scripts/gdb/linux/constants.py", line 2, in <module>
      LX_CLK_GET_RATE_NOCACHE = gdb.parse_and_eval("CLK_GET_RATE_NOCACHE")
  gdb.error: No symbol "CLK_GET_RATE_NOCACHE" in current context.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: e7e6f46 ("scripts/gdb: print cached rate in lx-clk-summary")
Signed-off-by: Fabiano Rosas <[email protected]>
Reviewed-by: Stephen Boyd <[email protected]>
Cc: Jan Kiszka <[email protected]>
Cc: Kieran Bingham <[email protected]>
Cc: Leonard Crestez <[email protected]>
Cc: Jackie Liu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

scripts/gdb/linux/constants.py.in

@@ -40,7 +40,8 @@
 import gdb
 
 /* linux/clk-provider.h */
-LX_GDBPARSED(CLK_GET_RATE_NOCACHE)
+if IS_BUILTIN(CONFIG_COMMON_CLK):
+    LX_GDBPARSED(CLK_GET_RATE_NOCACHE)
 
 /* linux/fs.h */
 LX_VALUE(SB_RDONLY)