mips: Do not include hi and lo in __SYSCALL_CLOBBERS for R6

From [1]
"GCC 10 (PR 91233) won't silently allow registers that are not architecturally
available to be present in the clobber list anymore, resulting in build failure
for mips*r6 targets in form of:
...
.../sysdep.h:146:2: error: the register ‘lo’ cannot be clobbered in ‘asm’ for the current target
  146 |  __asm__ volatile (      \
      |  ^~~~~~~

This is because base R6 ISA doesn't define hi and lo registers w/o DSP extension.
This patch provides the alternative definitions of __SYSCALL_CLOBBERS for r6
targets that won't include those registers."

[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=020b2a97bb15f807c0482f0faee2184ed05bcad8

Signed-off-by: Romain Naour <romain.naour@gmail.com>
Cc: Waldemar Brodkorb <wbx@openadk.org>

libc/sysdeps/linux/mips/bits/syscalls.h

@@ -270,8 +270,13 @@
 	_sys_result;							\
 })
 
-#define __SYSCALL_CLOBBERS "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13", \
-	"$14", "$15", "$24", "$25", "hi", "lo", "memory"
+#if __mips_isa_rev >= 6
+# define __SYSCALL_CLOBBERS "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13", \
+	 "$14", "$15", "$24", "$25", "memory"
+#else
+# define __SYSCALL_CLOBBERS "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13", \
+	 "$14", "$15", "$24", "$25", "hi", "lo", "memory"
+#endif
 
 #else /* N32 || N64 */
 
@@ -327,8 +332,13 @@
 	_sys_result;							\
 })
 
-#define __SYSCALL_CLOBBERS "$1", "$3", "$10", "$11", "$12", "$13", \
-	"$14", "$15", "$24", "$25", "hi", "lo", "memory"
+#if __mips_isa_rev >= 6
+# define __SYSCALL_CLOBBERS "$1", "$3", "$10", "$11", "$12", "$13", \
+	 "$14", "$15", "$24", "$25", "memory"
+#else
+# define __SYSCALL_CLOBBERS "$1", "$3", "$10", "$11", "$12", "$13", \
+	 "$14", "$15", "$24", "$25", "hi", "lo", "memory"
+#endif
 
 #endif