arm hostfs: Compile only when enabled by config (#307)

* arch/arm/src/tiva/Make.defs: Compile only when enabled by configuration CONFIG_ARM_SEMIHOSTING_HOSTFS
*  arch/arm/src/common/up_hostfs.c:  Remove the ifdef conditional because it's redundant with the make logic.

arch/arm/src/common/up_hostfs.c

@@ -46,8 +46,6 @@
 #include <syscall.h>
 #include <unistd.h>
 
-#ifdef CONFIG_ARM_SEMIHOSTING_HOSTFS
-
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
@@ -328,5 +326,3 @@ int host_stat(const char *path, struct stat *buf)
 
   return ret;
 }
-
-#endif

arch/arm/src/tiva/Make.defs

@@ -53,7 +53,10 @@ CMN_CSRCS += up_releasepending.c up_releasestack.c up_reprioritizertr.c
 CMN_CSRCS += up_schedulesigaction.c up_sigdeliver.c up_stackframe.c
 CMN_CSRCS += up_svcall.c up_trigger_irq.c up_unblocktask.c up_udelay.c
 CMN_CSRCS += up_usestack.c up_vfork.c
-CMN_CSRCS += up_hostfs.c
+
+ifeq ($(CONFIG_ARM_SEMIHOSTING_HOSTFS),y)
+  CMN_CSRCS += up_hostfs.c
+endif
 
 ifneq ($(CONFIG_ARCH_IDLE_CUSTOM),y)
   CMN_CSRCS += up_idle.c