Kendryte build warnings

[Heinrich Schuchardt]

Hello Sean,

when I compile for Kendryte K210 I see the following build warnings:

In file included from drivers/clk/kendryte/clk.c:15:
include/kendryte/pll.h:46: warning: "nop" redefined
   46 | #define nop()
      |
In file included from ./arch/riscv/include/asm/io.h:13,
                 from drivers/clk/kendryte/clk.c:7:
./arch/riscv/include/asm/barrier.h:16: note: this is the location of the
previous definition
   16 | #define nop()  __asm__ __volatile__ ("nop")
      |
In file included from ./arch/riscv/include/asm/io.h:13,
                 from drivers/clk/kendryte/pll.c:8:
./arch/riscv/include/asm/barrier.h:16: warning: "nop" redefined
   16 | #define nop()  __asm__ __volatile__ ("nop")
      |
In file included from drivers/clk/kendryte/pll.c:6:
include/kendryte/pll.h:46: note: this is the location of the previous
definition
   46 | #define nop()
      |

Should nop() be the assembler instruction nop or nothing?

Best regards

Heinrich