MDEV-39692 innodb intrinsics fail to compile on ARMv8.3-A and later (but not ARMv9.x)

Assembler messages:
{standard input}:169: Error: selected processor does not support `retaa'
{standard input}:271: Error: selected processor does not support `retaa'

It happens because the pmem_cvap() funciton manually inserts the `.arch
armv8-2.a` clause, making GAS believe that retaa instruction (inserted
by GCC) is invalid.

Replaced compiler dependent version by using the generic sys instruction:

__asm__ __volatile__(/* dc cvap, %0 */ "sys #3, c7, c12, 1, %0" ::
                           "r"(u) : "memory");

Co-authored-by: gemini-code-assist
Reported-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Marko Mäkelä

Original solution: https://lore.kernel.org/openembedded-devel/20260520113418.2523208-1-dmitry.baryshkov@oss.qualcomm.com/

Author: grooverdan

storage/innobase/sync/cache.cc

@@ -82,11 +82,8 @@ static void pmem_cvap(const void* buf, size_t size)
   for (uintptr_t u= uintptr_t(buf) & ~(CPU_LEVEL1_DCACHE_LINESIZE),
          end= uintptr_t(buf) + size;
        u < end; u+= CPU_LEVEL1_DCACHE_LINESIZE)
-#if defined __ARM_ARCH && __ARM_ARCH == 9
-    __asm__ __volatile__(".arch armv9.4-a\n dc cvap, %0" :: "r"(u) : "memory");
-#else
-    __asm__ __volatile__(".arch armv8.2-a\n dc cvap, %0" :: "r"(u) : "memory");
-#endif
+    __asm__ __volatile__(/* dc cvap, %0 */ "sys #3, c7, c12, 1, %0" ::
+                         "r"(u) : "memory");
 
   __asm__ __volatile__("dmb ishst" ::: "memory");
 }