src/*: Specify type of DIMM_MAX once

Specify the type of the `DIMM_MAX` Kconfig symbol once.

Change-Id: I2e86baaa8bd50c7b82c399fde5dcea05da6b4307
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57258
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Tim Crawford <tcrawford@system76.com>
Reviewed-by:  Felix Singer <felixsinger@posteo.net>

src/soc/intel/xeon_sp/cpx/Kconfig

@@ -105,7 +105,6 @@ config CPU_BCLK_MHZ
 # CPX-SP has 2 IMCs, 3 channels per IMC, 2 DIMMs per channel
 # Default value is set to one socket, full config.
 config DIMM_MAX
-	int
 	default 12
 
 # DDR4