sconfig: Add support for firmware configuration

This change adds support to sconfig for generating the firmware
configuration field and option definitions in devicetree.cb.

In addition these fields and options can be used to probe for a device
and have that device be disabled if it is not found at boot time.

New tokens:
fw_config: top level token, table can be defined before chips
field: define field in the mask with the start and end bits
option: define option in a field with the value of the field
probe: indicate that a device should probe by field and option

Example:
fw_config
    field FEATURE 0 0
        option DISABLE 0
        option ENABLE 1
    end
end
chip drivers/generic/feature
    device generic 0 on
        probe FEATURE ENABLE
    end
end

Variants can add new fields and add new options to existing fields in
overridetree.cb but cannot redefine an existing option.

Devices can have multiple probe tokens, and the device will be considered
to be found if any of them return true.

The output from defining this field are:

1) the various fields and options will be added as macro constants to
static.h and can be used by fw_config for probing.
2) the probe entries will result in a list of fields/options to probe
that is added to the resulting struct device and handled by coreboot.

BUG=b:147462631

Signed-off-by: Duncan Laurie <dlaurie@google.com>
Change-Id: I8aea63e577d933aea09e0d0b09470929cc96e0de
Reviewed-on: https://review.coreboot.org/c/coreboot/+/41440
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

util/sconfig/sconfig.l

@@ -14,6 +14,10 @@ int linenum = 0;
 chip			{return(CHIP);}
 device			{return(DEVICE);}
 register		{return(REGISTER);}
+fw_config		{return(FW_CONFIG_TABLE);}
+field			{return(FW_CONFIG_FIELD);}
+option			{return(FW_CONFIG_OPTION);}
+probe			{return(FW_CONFIG_PROBE);}
 on			{yylval.number=1; return(BOOL);}
 off			{yylval.number=0; return(BOOL);}
 hidden			{yylval.number=3; return(STATUS);}