linux-user: Check dump_write() return in elf_core_dump()

One of the calls to dump_write() in elf_core_dump() was missing
a check for failure (spotted by Coverity). Add the check to
bring it into line with the other calls from this function.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NRiku Voipio <riku.voipio@linaro.org>

linux-user/elfload.c

@@ -3050,7 +3050,9 @@ static int elf_core_dump(int signr, const CPUArchState *env)
         phdr.p_align = ELF_EXEC_PAGESIZE;
 
         bswap_phdr(&phdr, 1);
-        dump_write(fd, &phdr, sizeof (phdr));
+        if (dump_write(fd, &phdr, sizeof(phdr)) != 0) {
+            goto out;
+        }
     }
 
     /*