microchip: espi: Fix bug in dependency on ESPI Kconfig

`Kconfig.xec` for the ESPI drivers requires
DT_HAS_MICROCHIP_XEC_ESPI_SAF_ENABLED and
DT_HAS_MICROCHIP_XEC_ESPI_SAF_V2_ENABLED for ESPI_XEC and ESPI_XEC_V2,
respectively, but SAF is not mandatory for using ESPI. This is a bug and
should be dependent on DT_HAS_MICROCHIP_XEC_ESPI_ENABLED and
DT_HAS_MICROCHIP_XEC_ESPI_ENABLED, respectively. Also make these default
to `y` so they can be automatically enabled by the device tree.

Signed-off-by: Tristan Honscheid <honscheid@google.com>