arch/arm/gd32f4: fix missing CTL selector bits in up_disableusartint.

[lccosy]

Summary

Fix a bug in up_disableusartint() where USART interrupt state is saved without CTL selector bits (bits 24-27), causing up_restoreusartint() to never restore interrupt enables.

Problem

up_disableusartint() saves interrupt state from hardware CTL0-CTL3 registers into an encoded ie value, but omits the CTL selector bits. When up_restoreusartint() later restores interrupts using ie >> 24 to determine which CTL register to write, this evaluates to 0, so no CTL register is updated and all interrupt enables (including RBNEIE) are permanently lost.

This causes RX interrupts to never fire after any call to up_putc() (e.g. via syslog), making the serial console unable to receive input on GD32F4 platforms.

Impact

• Serial console TX works normally (output is visible)
• Serial console RX is completely broken (no input accepted, no NSH prompt)
• Affects all GD32F4 USART ports when syslog or up_putc() is used

Fix

Add the corresponding CTL selector bit ( USART_CFG_CTLx_INT << USART_CFG_SHIFT ) whenever a CTL register has active interrupt bits, so that up_restoreusartint() can correctly identify and restore the interrupt state.

Testing

Tested on mplant-gd32f450 custom board (GD32F450ZGT6) with USART5 as serial console:

• Before fix: NSH can output debug prints but cannot accept input, no
  sh>\ prompt , like this

ASERIAL: up_setup done base=0x40011400 CTL0=0x0000200c BAUD=0x00000364
BD
SERIAL: up_attach base=0x40011400 irq=87
SERIAL: up_attach IRQ87 enabled OK
SERIAL: up_rxint enable=1 base=0x40011400 ie=0x00000000
SERIAL: up_rxint done ie=0x01000002
bringup: USART5@0x40011400
  STAT0=0x00000000

• After fix: NSH works correctly with both input and output,
  sh>\ prompt appears, like this

Nuttheartbeat: led task running
Shell (NSH)
Board: mplant-gd32f450 (GD32F450IK)
MCU:  GD32F450 200MHz, 112 KB SRAM

nsh>