sw_isr_table: Add spaces to fix compiler warning

When using clang to build a C++ file that includes this file, it warns:

include/zephyr/sw_isr_table.h:195:28: error: invalid suffix on literal;
C++11 requires a space between literal and identifier
[-Wreserved-user-defined-literal]
         "." Z_STRINGIFY(prefix)"."file"." Z_STRINGIFY(counter)

Signed-off-by: Tom Hughes <tomhughes@chromium.org>

Author: thughes

include/zephyr/sw_isr_table.h

@@ -191,8 +191,8 @@ extern struct z_shared_isr_table_entry z_shared_sw_isr_table[];
 #define _MK_IRQ_ELEMENT_NAME(func, id) __MK_ISR_ELEMENT_NAME(func, id)
 #define __MK_IRQ_ELEMENT_NAME(func, id) __irq_table_entry_ ## func ## _irq_ ## id
 
-#define _MK_ISR_SECTION_NAME(prefix, file, counter) \
-	"." Z_STRINGIFY(prefix)"."file"." Z_STRINGIFY(counter)
+#define _MK_ISR_SECTION_NAME(prefix, file, counter)                                                \
+	"." Z_STRINGIFY(prefix) "." file "." Z_STRINGIFY(counter)
 
 #define _MK_ISR_ELEMENT_SECTION(counter) _MK_ISR_SECTION_NAME(irq, __FILE__, counter)
 #define _MK_IRQ_ELEMENT_SECTION(counter) _MK_ISR_SECTION_NAME(isr, __FILE__, counter)