s390: fix clang -Wpointer-sign warnigns in boot code

The arch/s390/boot directory is built with its own set of compiler
options that does not include -Wno-pointer-sign like the rest of
the kernel does, this causes a lot of harmless but correct warnings
when building with clang.

For the atomics, we can add type casts to avoid the warnings, for
everything else the easiest way is to slightly adapt the types
to be more consistent.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/char/sclp.h

@@ -367,14 +367,14 @@ sclp_ascebc(unsigned char ch)
 
 /* translate string from EBCDIC to ASCII */
 static inline void
-sclp_ebcasc_str(unsigned char *str, int nr)
+sclp_ebcasc_str(char *str, int nr)
 {
 	(MACHINE_IS_VM) ? EBCASC(str, nr) : EBCASC_500(str, nr);
 }
 
 /* translate string from ASCII to EBCDIC */
 static inline void
-sclp_ascebc_str(unsigned char *str, int nr)
+sclp_ascebc_str(char *str, int nr)
 {
 	(MACHINE_IS_VM) ? ASCEBC(str, nr) : ASCEBC_500(str, nr);
 }