[builtins] Fix value of ARM_INEXACT

The existing value of 0x1000 sets the IXE bit (Inexact floating-point exception
trap enable), but we really want to be setting IXC, bit 4:
Inexact cumulative floating-point exception bit. This bit is set to 1 to
indicate that the Inexact floating-point exception has occurred since 0 was
last written to this bit.

Reviewed By: kongyi, peter.smith
Differential Revision: https://reviews.llvm.org/D98353

compiler-rt/lib/builtins/arm/fp_mode.c

@@ -18,7 +18,7 @@
                         ARM_DOWNWARD | ARM_TOWARDZERO)
 #define ARM_RMODE_SHIFT 22
 
-#define ARM_INEXACT     0x1000
+#define ARM_INEXACT     0x10
 
 #ifndef __ARM_FP
 // For soft float targets, allow changing rounding mode by overriding the weak