commonlib: Add CBMEM ID to store boot mode

Introduce a new CBMEM ID, CBMEM_ID_BOOT_MODE (0x444D5442, "BTMD"),
to provide a dedicated storage location for the system's detected
boot mode (e.g., normal boot, low-battery, off-mode boot etc).

Storing the boot mode in CBMEM ensures that the initial detection
performed early in the boot process (e.g., in romstage by reading
PMIC logs) is securely passed to subsequent stages like ramstage,
where different boot modes require distinct logic paths.

Key changes:
- Define CBMEM_ID_BOOT_MODE in cbmem_id.h.
- Add "BOOT MODE" entry to the CBMEM_ID_TO_NAME_TABLE.

BUG=b:439819922
TEST=Verify boot mode stored in CBMEM.

Change-Id: I7ebf29385a99ac1be491bfefe1c74c8c9e58b55d
Signed-off-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/90175
Reviewed-by: Subrata Banik <subratabanik@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/commonlib/bsd/include/commonlib/bsd/cbmem_id.h

@@ -91,6 +91,7 @@
 #define CBMEM_ID_CSE_BP_INFO	0x42455343
 #define CBMEM_ID_AMD_OPENSIL	0x4153494C
 #define CBMEM_ID_PVMFW		0x666d7670
+#define CBMEM_ID_BOOT_MODE	0x444D5442
 
 #define CBMEM_ID_TO_NAME_TABLE				 \
 	{ CBMEM_ID_ACPI,		"ACPI       " }, \
@@ -174,5 +175,6 @@
 	{ CBMEM_ID_CSE_INFO,		"CSE SPECIFIC INFO"},\
 	{ CBMEM_ID_CSE_BP_INFO,		"CSE BP INFO"}, \
 	{ CBMEM_ID_AMD_OPENSIL,		"OPENSIL DATA"}, \
-	{ CBMEM_ID_PVMFW,		"PVMFW      "}
+	{ CBMEM_ID_PVMFW,		"PVMFW      "}, \
+	{ CBMEM_ID_BOOT_MODE,		"BOOT MODE  "}
 #endif /* _CBMEM_ID_H_ */