vl: fix memory leak in configure_accelerators

vl: fix memory leak in configure_accelerators

The accel_list forgot to free, the asan output:

Direct leak of 16 byte(s) in 1 object(s) allocated from:
    #0 0xffff919331cb in __interceptor_malloc (/lib64/libasan.so.4+0xd31cb)
    #1 0xffff913f7163 in g_malloc (/lib64/libglib-2.0.so.0+0x57163)
    #2 0xffff91413d9b in g_strsplit (/lib64/libglib-2.0.so.0+0x73d9b)
    #3 0xaaab42fb58e7 in configure_accelerators /qemu/vl.c:2777
    #4 0xaaab42fb58e7 in main /qemu/vl.c:4121
    #5 0xffff8f9b0b9f in __libc_start_main (/lib64/libc.so.6+0x20b9f)
    #6 0xaaab42fc1dab  (/qemu/build/aarch64-softmmu/qemu-system-aarch64+0x8b1dab)

Indirect leak of 4 byte(s) in 1 object(s) allocated from:
    #0 0xffff919331cb in __interceptor_malloc (/lib64/libasan.so.4+0xd31cb)
    #1 0xffff913f7163 in g_malloc (/lib64/libglib-2.0.so.0+0x57163)
    #2 0xffff9141243b in g_strdup (/lib64/libglib-2.0.so.0+0x7243b)
    #3 0xffff91413e6f in g_strsplit (/lib64/libglib-2.0.so.0+0x73e6f)
    #4 0xaaab42fb58e7 in configure_accelerators /qemu/vl.c:2777
    #5 0xaaab42fb58e7 in main /qemu/vl.c:4121
    #6 0xffff8f9b0b9f in __libc_start_main (/lib64/libc.so.6+0x20b9f)
    #7 0xaaab42fc1dab  (/qemu/build/aarch64-softmmu/qemu-system-aarch64+0x8b1dab)

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200108114207.58084-1-kuhn.chenqun@huawei.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>