hw/sd/sdcard: Remove ACMD6 handler for SPI mode

There is no ACMD6 command in SPI mode, remove the pointless
handler introduced in commit 946897ce18 ("sdcard: handles
more commands in SPI mode"). Keep sd_cmd_unimplemented()
since we'll reuse it later.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Tested-by: Cédric Le Goater <clg@redhat.com>
Message-Id: <20240621080554.18986-8-philmd@linaro.org>
diff --git a/hw/sd/sd.c b/hw/sd/sd.c
index 6e346e2..08a6d0a 100644
--- a/hw/sd/sd.c
+++ b/hw/sd/sd.c
@@ -1012,6 +1012,7 @@
 }
 
 /* Commands that are recognised but not yet implemented. */
+__attribute__((unused))
 static sd_rsp_type_t sd_cmd_unimplemented(SDState *sd, SDRequest req)
 {
     qemu_log_mask(LOG_UNIMP, "%s: CMD%i not implemented\n",
@@ -2154,7 +2155,6 @@
         [52 ... 54] = sd_cmd_illegal,
     },
     .acmd = {
-        [6]         = sd_cmd_unimplemented,
         [41]        = spi_cmd_SEND_OP_COND,
     },
 };