USB: gadget: u_f: Unbreak offset calculation in VLAs

Inadvertently the commit b1cd1b65af ("USB: gadget: u_f: add overflow checks
to VLA macros") makes VLA macros to always return 0 due to different scope of
two variables of the same name. Obviously we need to have only one.

Fixes: b1cd1b65af ("USB: gadget: u_f: add overflow checks to VLA macros")
Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Brooke Basile <brookebasile@gmail.com>
Cc: stable <stable@kernel.org>
Link: https://lore.kernel.org/r/20200826192119.56450-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/gadget/u_f.h

@@ -25,9 +25,9 @@
 		size_t offset = 0;					       \
 		if (groupname##__next != SIZE_MAX) {			       \
 			size_t align_mask = __alignof__(type) - 1;	       \
-			size_t offset = (groupname##__next + align_mask)       \
-					 & ~align_mask;			       \
 			size_t size = array_size(n, sizeof(type));	       \
+			offset = (groupname##__next + align_mask) &	       \
+				  ~align_mask;				       \
 			if (check_add_overflow(offset, size,		       \
 					       &groupname##__next)) {          \
 				groupname##__next = SIZE_MAX;		       \
@@ -43,8 +43,8 @@
 		size_t offset = 0;						\
 		if (groupname##__next != SIZE_MAX) {				\
 			size_t align_mask = __alignof__(type) - 1;		\
-			size_t offset = (groupname##__next + align_mask)	\
-					 & ~align_mask;				\
+			offset = (groupname##__next + align_mask) &		\
+				  ~align_mask;					\
 			if (check_add_overflow(offset, groupname##_##name##__sz,\
 							&groupname##__next)) {	\
 				groupname##__next = SIZE_MAX;			\