uapi/auxvec: Define the aux vector AT_MINSIGSTKSZ

Define AT_MINSIGSTKSZ in the generic uapi header. It is already used
as generic ABI in glibc's generic elf.h, and this define will prevent
future namespace conflicts. In particular, x86 is also using this
generic definition.
Signed-off-by: NChang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Reviewed-by: NLen Brown <len.brown@intel.com>
Acked-by: NThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20210518200320.17239-2-chang.seok.bae@intel.com

include/uapi/linux/auxvec.h

@@ -33,5 +33,8 @@
 
 #define AT_EXECFN  31	/* filename of program */
 
+#ifndef AT_MINSIGSTKSZ
+#define AT_MINSIGSTKSZ	51	/* minimal stack size for signal delivery */
+#endif
 
 #endif /* _UAPI_LINUX_AUXVEC_H */