x86/percpu: Make CONFIG_USE_X86_SEG_SUPPORT work with sparse

Now that sparse builds enforce the usage of typeof_unqual() the casts in
__raw_cpu_read/write() cause sparse to emit tons of false postive
warnings:

 warning: cast removes address space '__percpu' of expression

Address this by annotating the casts with __force.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/87v7gz0yjv.ffs@tglx
Closes: https://lore.kernel.org/oe-kbuild-all/202601181733.YZOf9XU3-lkp@intel.com/

Author: Thomas Gleixner

arch/x86/include/asm/percpu.h

@@ -137,12 +137,12 @@
 
 #define __raw_cpu_read(size, qual, pcp)					\
 ({									\
-	*(qual __my_cpu_type(pcp) *)__my_cpu_ptr(&(pcp));		\
+	*(qual __my_cpu_type(pcp) * __force)__my_cpu_ptr(&(pcp));	\
 })
 
-#define __raw_cpu_write(size, qual, pcp, val)				\
-do {									\
-	*(qual __my_cpu_type(pcp) *)__my_cpu_ptr(&(pcp)) = (val);	\
+#define __raw_cpu_write(size, qual, pcp, val)					\
+do {										\
+	*(qual __my_cpu_type(pcp) * __force)__my_cpu_ptr(&(pcp)) = (val);	\
 } while (0)
 
 #define __raw_cpu_read_const(pcp)	__raw_cpu_read(, , pcp)