clk: stm32f4: fix post divisor setup for I2S/SAI PLLs

Enabling the framebuffer leads to a system hang. Running, as a debug
hack, the store_pan() function in drivers/video/fbdev/core/fbsysfs.c
without taking the console_lock, allows to see the crash backtrace on
the serial line.

~ # echo 0 0 > /sys/class/graphics/fb0/pan

[    9.719414] Unhandled exception: IPSR = 00000005 LR = fffffff1
[    9.726937] CPU: 0 PID: 49 Comm: sh Not tainted 5.13.0-rc5 #9
[    9.733008] Hardware name: STM32 (Device Tree Support)
[    9.738296] PC is at clk_gate_is_enabled+0x0/0x28
[    9.743426] LR is at stm32f4_pll_div_set_rate+0xf/0x38
[    9.748857] pc : [<0011e4be>]    lr : [<0011f9e3>]    psr: 0100000b
[    9.755373] sp : 00bc7be0  ip : 00000000  fp : 001f3ac4
[    9.760812] r10: 002610d0  r9 : 01efe920  r8 : 00540560
[    9.766269] r7 : 02e7ddb0  r6 : 0173eed8  r5 : 00000000  r4 : 004027c0
[    9.773081] r3 : 0011e4bf  r2 : 02e7ddb0  r1 : 0173eed8  r0 : 1d3267b8
[    9.779911] xPSR: 0100000b
[    9.782719] CPU: 0 PID: 49 Comm: sh Not tainted 5.13.0-rc5 #9
[    9.788791] Hardware name: STM32 (Device Tree Support)
[    9.794120] [<0000afa1>] (unwind_backtrace) from [<0000a33f>] (show_stack+0xb/0xc)
[    9.802421] [<0000a33f>] (show_stack) from [<0000a8df>] (__invalid_entry+0x4b/0x4c)

The `pll_num' field in the post_div_data configuration contained a wrong
value which also referenced an uninitialized hardware clock when
clk_register_pll_div() was called.

Fixes: 517633ef ("clk: stm32f4: Add post divisor for I2S & SAI PLLs")
Signed-off-by: Dario Binacchi <dariobin@libero.it>
Reviewed-by: Gabriel Fernandez <gabriel.fernandez@st.com>
Link: https://lore.kernel.org/r/20210725160725.10788-1-dariobin@libero.it


Signed-off-by: Stephen Boyd <sboyd@kernel.org>