FPE in npcm7xx_clk_update_pll

This was originally reported at: https://bugs.launchpad.net/qemu/+bug/1913667

Hello,

Reproducer

cat << EOF | ./qemu-system-aarch64 -M npcm750-evb \
-accel qtest -qtest stdio
write 0xf080100c 0x4 0x00
write 0xf080100c 0x4 0x00
EOF

Stack-Trace

../hw/misc/npcm7xx_clk.c:131:14: runtime error: division by zero
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior ../hw/misc/npcm7xx_clk.c:131:14 in
AddressSanitizer:DEADLYSIGNAL
=================================================================
==717855==ERROR: AddressSanitizer: FPE on unknown address 0x5619201fcd8c (pc 0x5619201fcd8c bp 0x7ffc94214e50 sp 0x7ffc94214e30 T0)
#0 0x5619201fcd8c in npcm7xx_clk_update_pll /hw/misc/npcm7xx_clk.c:131:14
#1 0x5619201ff5dc in npcm7xx_clk_write /hw/misc/npcm7xx_clk.c:799:13
#2 0x5619214781fe in memory_region_write_accessor /softmmu/memory.c:491:5
#3 0x561921477bfb in access_with_adjusted_size /softmmu/memory.c:552:18
#4 0x561921477467 in memory_region_dispatch_write /softmmu/memory.c
#5 0x561921807ffb in flatview_write_continue /softmmu/physmem.c:2759:23
#6 0x5619217fd71b in flatview_write /softmmu/physmem.c:2799:14
#7 0x5619217fd71b in address_space_write /softmmu/physmem.c:2891:18
#8 0x561921465eee in qtest_process_command /softmmu/qtest.c:539:13
#9 0x561921462b97 in qtest_process_inbuf /softmmu/qtest.c:797:9
#10 0x561921cb3286 in fd_chr_read /chardev/char-fd.c:68:9
#11 0x7f4ad283baae in g_main_context_dispatch (/usr/lib/x86_64-linux-gnu/libglib-2.0.so.0+0x51aae)
#12 0x56192230e363 in glib_pollfds_poll /util/main-loop.c:232:9
#13 0x56192230e363 in os_host_main_loop_wait /util/main-loop.c:255:5
#14 0x56192230e363 in main_loop_wait /util/main-loop.c:531:11
#15 0x5619213c9599 in qemu_main_loop /softmmu/runstate.c:721:9
#16 0x56191f6561fd in main /softmmu/main.c:50:5
#17 0x7f4ad22e0cc9 in __libc_start_main csu/../csu/libc-start.c:308:16
#18 0x56191f5a9bc9 in _start (/home/alxndr/Development/qemu/build/qemu-system-aarch64+0x3350bc9)

Thank you