mainboards: Don’t select `CONSOLE_POST`

Currently, it’s impossible for the user to select `NO_POST`, for boards
selecting `CONSOLE_POST` in their config.

```
warning: (BOARD_SPECIFIC_OPTIONS) selects CONSOLE_POST which has unmet
direct dependencies (VENDOR_SIEMENS && BOARD_SIEMENS_MC_BDX1 || !NO_POST)
```

This is currently done for Intel Camelback Mountain and Siemens MC-BDX1.

Selecting the option `CONSOLE_POST` in board specific configuration is
not a good idea, as this should be user configurable over Kconfig, and
also the tree-wide defaults should be the same for these options.

Kconfig is different, as commit 97535558f1 (mainboard/{google,intel}:
Change config option selection) only touch the Intel board.

Change-Id: I91c1e0cb92ed218b6bbc7c33759b91f748cf6f51
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/18878
Tested-by: build bot (Jenkins)
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>

src/mainboard/intel/camelbackmountain_fsp/Kconfig

@@ -10,7 +10,6 @@ config BOARD_SPECIFIC_OPTIONS
 	select INTEGRATED_UART if FSP_PACKAGE_DEFAULT
 	select HAVE_FSP_BIN if FSP_PACKAGE_DEFAULT
 	select SERIRQ_CONTINUOUS_MODE
-	select CONSOLE_POST
 
 config MAINBOARD_DIR
 	string

src/mainboard/siemens/mc_bdx1/Kconfig

@@ -38,10 +38,6 @@ config VIRTUAL_ROM_SIZE
 	hex
 	default 0x1000000
 
-config CONSOLE_POST
-	bool
-	default y
-
 config INTEGRATED_UART
 	bool
 	default n