soc/intel/{ehl,jsl}: make use of Kconfig options for PRMRR size

Migrate the last two platforms to using Kconfig through
`get_valid_prmrr_size()` instead of hardcoded values in the devicetree.

Change-Id: I93aa177f741ca8b2a2d50fae2515606b96784e83
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57674
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>

src/soc/intel/elkhartlake/chip.h

@@ -235,17 +235,9 @@ struct soc_intel_elkhartlake_config {
 
 	/* Enable C6 DRAM */
 	uint8_t enable_c6dram;
-	/*
-	 * PRMRR size setting with below options
-	 * Disable: 0x0
-	 * 32MB: 0x2000000
-	 * 64MB: 0x4000000
-	 * 128 MB: 0x8000000
-	 * 256 MB: 0x10000000
-	 * 512 MB: 0x20000000
-	 */
-	uint32_t PrmrrSize;
+
 	uint8_t PmTimerDisabled;
+
 	/*
 	 * SerialIO device mode selection:
 	 * PchSerialIoDisabled,