linux-user: drop __cygwin__ ifdef

linux-user doesn't work on cygwin anyways.

Cc: Richard Henderson <rth@twiddle.net>
Signed-off-by: NRiku Voipio <riku.voipio@linaro.org>

linux-user/mmap.c

@@ -193,9 +193,6 @@ static int mmap_frag(abi_ulong real_start,
 
 #if HOST_LONG_BITS == 64 && TARGET_ABI_BITS == 64
 # define TASK_UNMAPPED_BASE  (1ul << 38)
-#elif defined(__CYGWIN__)
-/* Cygwin doesn't have a whole lot of address space.  */
-# define TASK_UNMAPPED_BASE  0x18000000
 #else
 # define TASK_UNMAPPED_BASE  0x40000000
 #endif