sdmmc: fix malloc error handling in sdmmc_mem_send_scr()

[Tobias Heider]

sdmmc_mem_send_scr() tries to malloc() with M_NOWAIT and returns 0 on
error,  which leads to sdmmc_mem_sd_init() passing uninitialized stack
memory to sdmmc_mem_decode_scr().
The diff below makes sdmmc_mem_send_scr() return ENOMEM if malloc fails.

ok?

diff --git a/sys/dev/sdmmc/sdmmc_mem.c b/sys/dev/sdmmc/sdmmc_mem.c
index fae8d63912d..715c412e6ea 100644
--- a/sys/dev/sdmmc/sdmmc_mem.c
+++ b/sys/dev/sdmmc/sdmmc_mem.c
@@ -465,8 +465,10 @@ sdmmc_mem_send_scr(struct sdmmc_softc *sc, uint32_t *scr)
        int error = 0;
 
        ptr = malloc(datalen, M_DEVBUF, M_NOWAIT | M_ZERO);
-       if (ptr == NULL)
+       if (ptr == NULL) {
+               error = ENOMEM;
                goto out;
+       }
 
        memset(&cmd, 0, sizeof(cmd));
        cmd.c_data = ptr;