CC2538: Add CONF parameters to select boot loader backdoor pin and logic level.
Rename FLASH_CCA_CONF_BOOTLDR_BACKDOOR_PIN to FLASH_CCA_CONF_BOOTLDR_BACKDOOR_PORT_A_PIN.
Un-indent preprocessor directives.
Changes suggested by @bthebaudeau.
Merge pull request #641 from hexluthor/backdoor-conf

CC2538: Add CONF parameters to select boot loader backdoor pin and logic level