Revert "libobs: Improve util_mul_div64 outside MSVC"

This reverts commit c977417747992e3fed32b775073503b25fb82599.

Reverted due to a regression.

libobs/util/util_uint64.h

@@ -22,17 +22,7 @@
 
 static inline uint64_t util_mul_div64(uint64_t num, uint64_t mul, uint64_t div)
 {
-#if !defined(_MSC_VER)
-#if defined(__x86_64__)
-	uint64_t rax, rdx;
-	__asm__("mulq %2" : "=a"(rax), "=d"(rdx) : "r"(num), "a"(mul));
-	__asm__("divq %1" : "=a"(rax) : "r"(div), "a"(rax), "d"(rdx));
-	return rax;
-#else
-	return (uint64_t)(((__uint128_t)num * (__uint128_t)mul) /
-			  (__uint128_t)div);
-#endif
-#elif defined(_M_X64) && (_MSC_VER >= 1920)
+#if defined(_MSC_VER) && defined(_M_X64) && (_MSC_VER >= 1920)
 	unsigned __int64 high;
 	const unsigned __int64 low = _umul128(num, mul, &high);
 	unsigned __int64 rem;