ARM: dts: exynos: Increase minimal ACLK400_DISP1 frequency on Exynos542x

ARM: dts: exynos: Increase minimal ACLK400_DISP1 frequency on Exynos542x

ACLK400_DISP1 bus feeds some internal buses of the display subsystem, some
of which are also related to TV/Mixer hardware modules. When that bus
is set to 120MHz, Exynos Mixer is not able to properly handle two XRGB
display planes at FullHD-60MHz. DMA underrun happens, which in turn might
result in reading data out of the configured buffer, what causes IOMMU
page fault and kernel panic.

This change fixes the following IOMMU fault, observed, when 2 Mixer planes
were enabled:

exynos-sysmmu 14650000.sysmmu: 14450000.mixer: PAGE FAULT occurred at 0x20fe9000
------------[ cut here ]------------
kernel BUG at ../drivers/iommu/exynos-iommu.c:450!
Internal error: Oops - BUG: 0 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.0.0-00003-g1b03088168ea #149
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
PC is at exynos_sysmmu_irq+0x1c0/0x264
LR is at lock_is_held_type+0x44/0x64
...

Reported-by: Marian Mihailescu <mihailescu2m@gmail.com>
Fixes: 5d99cc59a3c6 ("ARM: dts: exynos: Move Exynos5250 and Exynos5420 nodes under soc")
Fixes: b04a62d3ade3 ("ARM: dts: exynos: Add bus nodes using VDD_INT for Exynos542x SoC")
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Change-Id: I3d2f341f5e89d4631401f653d0ad9e36f26f45ad