Correct hexagon "unwinder_private_data_size"

Discovered while porting libstd to hexagon-unknown-qurt: the
unwinder data size refers to the count of pointers in _Unwind_Exception but
when I put the value "35" intiially for hexagon linux, I incorrectly
considered the size of the exception context hexagon_thread_state_t
data structure.

Correct the value for hexagon linux and expand it to cover all
hexagon architecture instead.

Author: androm3da

library/unwind/src/libunwind.rs

@@ -78,8 +78,8 @@ pub const unwinder_private_data_size: usize = 20;
 #[cfg(all(target_arch = "wasm32", target_os = "linux"))]
 pub const unwinder_private_data_size: usize = 2;
 
-#[cfg(all(target_arch = "hexagon", target_os = "linux"))]
-pub const unwinder_private_data_size: usize = 35;
+#[cfg(target_arch = "hexagon")]
+pub const unwinder_private_data_size: usize = 5;
 
 #[cfg(any(target_arch = "loongarch32", target_arch = "loongarch64"))]
 pub const unwinder_private_data_size: usize = 2;