boards: renesas: dts: Various fixes

This commit should deal with fixing
various issues on the board's dts
overlay files:

1. PSRAM node was not enabled when
   display buffers were stored in
   psram and thus, raising linker
    error (overflow memory section).

2. Remove MIPI DBI read operations
   for the MIPI DBI driver. This is
   because not all drivers support
   read and most of the cases it does
   not have any practical usage.
   In addition, this might trigger
   conflicts with SPI sensors.
   If needed, users should explicitly
   enable read operations by defining
   an SPI device taking into consideration
   conflicts with SPI devices connected
   to the SPI bus.

3. Remove enabling the DMA driver.
   It should be enabled by default.

Signed-off-by: Ioannis Karachalios <ioannis.karachalios.px@renesas.com>