irqchip/renesas-rzg2l: Do not set TIEN and TINT source at the same time

As per the hardware team, TIEN and TINT source should not set at the same
time due to a possible hardware race leading to spurious IRQ.

Currently on some scenarios hardware settings for TINT detection is not in
sync with TINT source as the enable/disable overrides source setting value
leading to hardware inconsistent state. For eg: consider the case GPIOINT0
is used as TINT interrupt and configuring GPIOINT5 as edge type. During
rzg2l_irq_set_type(), TINT source for GPIOINT5 is set. On disable(),
clearing of the entire bytes of TINT source selection for GPIOINT5 is same
as GPIOINT0 with TIEN disabled. Apart from this during enable(), the
setting of GPIOINT5 with TIEN results in spurious IRQ as due to a HW race,
it is possible that IP can use the TIEN with previous source value
(GPIOINT0).

So, just update TIEN during enable/disable as TINT source is already set
during rzg2l_irq_set_type(). This will make the consistent hardware
settings for detection method tied with TINT source and allows to simplify
the code.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>