drivers: spi: esp32xx: Fix word size issue

This commit fixes the word size configuration issue
described in #54746 by considering the data frame size
when trasmitting in case the configuration is applied.

It also fixes an heap corruption problem when using
SPI DMA with a buffer that is not multiple of 32 bits
in lenght and GDMA instance in initialization.

Signed-off-by: Lucas Tamborrino <lucas.tamborrino@espressif.com>