spi: atmel-quadspi: add padcalib, 2xgclk, and dllon capabilities

spi: atmel-quadspi: add padcalib, 2xgclk, and dllon capabilities

Introduce capability flags for SoC-specific variations of the QuadSPI
controller:

  - has_padcalib: controller supports pad calibration
  - has_2xgclk: requires GCLK at half the data rate (2x clocking)
  - has_dllon: controller supports DLL clock

Set `has_padcalib` for Octal controllers that provide pad calibration
support. Use `has_2xgclk` for controllers that require the GCLK to run
at twice the data rate. Differentiate SoC integration variants with the
`has_dllon` flag and set it as needed.

Signed-off-by: Varshini Rajendran <varshini.rajendran@microchip.com>
Signed-off-by: Dharma Balasubiramani <dharma.b@microchip.com>
Link: https://patch.msgid.link/20250908-microchip-qspi-v2-3-8f3d69fdd5c9@microchip.com
Signed-off-by: Mark Brown <broonie@kernel.org>