clk: meson: align gxbb_32k_clk_sel number of parents with actual count

In the Linux kernel, the following vulnerability has been resolved:

clk: meson: align gxbb_32k_clk_sel number of parents with actual count

The following out-of-bounds read has been observed by Christian on a
GXBB WeTek Hub:
==================================================================
BUG: KASAN: global-out-of-bounds in __clk_register+0x1b70/0x2418
Read of size 8 at addr ffffd66320cf88e0 by task swapper/0/1

CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.0.0-rc5 #1 PREEMPT
Hardware name: WeTek Hub (DT)
Call trace:
show_stack+0x14/0x20 (C)
dump_stack_lvl+0x74/0x94
print_report+0x164/0x4b0
kasan_report+0x98/0xd8
__asan_report_load8_noabort+0x1c/0x24
__clk_register+0x1b70/0x2418
devm_clk_hw_register+0x74/0x15c
meson_clkc_init+0xd4/0x20c
meson_clkc_syscon_probe+0x5c/0x94
platform_probe+0xbc/0x17c
really_probe+0x184/0x844
__driver_probe_device+0x154/0x35c
driver_probe_device+0x60/0x188
__driver_attach+0x168/0x4a0
bus_for_each_dev+0xec/0x180
driver_attach+0x38/0x58
bus_add_driver+0x238/0x4c0
driver_register+0x150/0x388
__platform_driver_register+0x54/0x7c
gxbb_clkc_driver_init+0x18/0x20
do_one_initcall+0xb8/0x340
kernel_init_freeable+0x49c/0x52c
kernel_init+0x24/0x148
ret_from_fork+0x10/0x20

The buggy address belongs to the variable:
gxbb_32k_clk_parents+0x60/0x400

The buggy address belongs to a vmalloc virtual mapping
The buggy address belongs to the physical page:

Memory state around the buggy address:
ffffd66320cf8780: 00 00 00 00 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
ffffd66320cf8800: 00 04 f9 f9 f9 f9 f9 f9 00 04 f9 f9 f9 f9 f9 f9
>ffffd66320cf8880: 00 00 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9
^
ffffd66320cf8900: 00 01 f9 f9 f9 f9 f9 f9 00 06 f9 f9 f9 f9 f9 f9
ffffd66320cf8980: 00 00 02 f9 f9 f9 f9 f9 00 00 02 f9 f9 f9 f9 f9
==================================================================

Commit 7915d7d5407c ("clk: amlogic: gxbb: drop non existing 32k clock
parent") dropped a non-existing clock parent from the gxbb_32k_clk_sel
mux but didn't adjust the hard-coded num_parents field. Fix the actual
number of parents of that mux by using ARRAY_SIZE instead (avoiding
similar problems in future).