[efi] Accept (and ignore) R_ARM_V4BX relocations

Relocation type R_ARM_V4BX requires no computation.  It marks the
location of an ARMv4 branch exchange instruction.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Modified-by: Michael Brown <mcb30@ipxe.org>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/util/elf2efi.c

 		case ELF_MREL ( EM_ARM, R_ARM_CALL ) :
 		case ELF_MREL ( EM_ARM, R_ARM_THM_PC22 ) :
 		case ELF_MREL ( EM_ARM, R_ARM_THM_JUMP24 ) :
+		case ELF_MREL ( EM_ARM, R_ARM_V4BX ):
 		case ELF_MREL ( EM_X86_64, R_X86_64_PC32 ) :
 		case ELF_MREL ( EM_AARCH64, R_AARCH64_CALL26 ) :
 		case ELF_MREL ( EM_AARCH64, R_AARCH64_JUMP26 ) :