hw/scsi/lsi53c895a: fix memory leak in lsi_scsi_realize()

hw/scsi/lsi53c895a: fix memory leak in lsi_scsi_realize()

Address a memory leak bug in the usages of timer_del().

The issue arises from the incorrect use of the ambiguous timer API
timer_del(), which does not free the timer object. The LeakSanitizer
report this issue during fuzzing. The correct API timer_free() freed
the timer object instead.

=================================================================
==2586273==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 48 byte(s) in 1 object(s) allocated from:
    #0 0x55f2afd89879 in calloc /llvm-project/compiler-rt/lib/asan/asan_malloc_linux.cpp:75:3
    #1 0x7f443b93ac50 in g_malloc0 (/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x5ec50)
    #2 0x55f2b053962e in timer_new include/qemu/timer.h:542:12
    #3 0x55f2b0514771 in timer_new_us include/qemu/timer.h:582:12
    #4 0x55f2b0514288 in lsi_scsi_realize hw/scsi/lsi53c895a.c:2350:24
    #5 0x55f2b0452d26 in pci_qdev_realize hw/pci/pci.c:2174:9

Signed-off-by: Zheng Huang <hz1624917200@outlook.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <73cd69f9-ff9b-4cd4-b8aa-265f9d6067b9@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>