rmodtool: add support for ARM

Add support for creating ARM rmodules. There are 3 expected
relocations for an ARM rmodule:
- R_ARM_ABS32
- R_ARM_THM_PC22
- R_ARM_THM_JUMP24

R_ARM_ABS32 is the only type that needs to emitted for relocation
as the other 2 are relative relocations.

BUG=chrome-os-partner:27094
BRANCH=None
TEST=Built vbootstub for ARM device.

Original-Change-Id: I0c22d4abca970e82ccd60b33fed700b96e3e52fb
Original-Signed-off-by: Aaron Durbin <adurbin@chromuim.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/190922
Original-Reviewed-by: Gabe Black <gabeblack@chromium.org>
(cherry picked from commit a642102ba7ace5c1829abe7732199eda6646950a)
Signed-off-by: Marc Jones <marc.jones@se-eng.com>

Change-Id: Ib3b3c90ebb672d8d6a537df896b97dc82c6186cc
Reviewed-on: http://review.coreboot.org/7204
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>

util/cbfstool/elf.h

@@ -2222,6 +2222,7 @@ typedef Elf32_Addr Elf32_Conflict;
 #define R_ARM_GOTPC		25	/* 32 bit PC relative offset to GOT */
 #define R_ARM_GOT32		26	/* 32 bit GOT entry */
 #define R_ARM_PLT32		27	/* 32 bit PLT address */
+#define R_ARM_THM_JUMP24	30
 #define R_ARM_ALU_PCREL_7_0	32
 #define R_ARM_ALU_PCREL_15_8	33
 #define R_ARM_ALU_PCREL_23_15	34