hexagon: fix fadvise64_64 calling conventions

fadvise64_64() has two 64-bit arguments at the wrong alignment
for hexagon, which turns them into a 7-argument syscall that is
not supported by Linux.

The downstream musl port for hexagon actually asks for a 6-argument
version the same way we do it on arm, csky, powerpc, so make the
kernel do it the same way to avoid having to change both.

Link: https://github.com/quic/musl/blob/hexagon/arch/hexagon/syscall_arch.h#L78
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Author: arndb

arch/hexagon/include/asm/syscalls.h

@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#include <asm-generic/syscalls.h>
+
+asmlinkage long sys_hexagon_fadvise64_64(int fd, int advice,
+	                                  u32 a2, u32 a3, u32 a4, u32 a5);

arch/hexagon/kernel/syscalltab.c

@@ -14,6 +14,13 @@
 #undef __SYSCALL
 #define __SYSCALL(nr, call) [nr] = (call),
 
+SYSCALL_DEFINE6(hexagon_fadvise64_64, int, fd, int, advice,
+		SC_ARG64(offset), SC_ARG64(len))
+{
+	return ksys_fadvise64_64(fd, SC_VAL64(loff_t, offset), SC_VAL64(loff_t, len), advice);
+}
+#define sys_fadvise64_64 sys_hexagon_fadvise64_64
+
 void *sys_call_table[__NR_syscalls] = {
 #include <asm/unistd.h>
 };