powerpc/prom_init: Move custom isspace() to its own namespace

If by some reason any of the headers will include ctype.h
we will have a name collision. Avoid this by moving isspace()
to the dedicate namespace.

First appearance of the code is in the commit cf68787b
("powerpc/prom_init: Evaluate mem kernel parameter for early allocation").
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
[mpe: Reformat prom_isxdigit() now that we allow longer lines]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210510144925.58195-1-andriy.shevchenko@linux.intel.com

arch/powerpc/kernel/prom_init.c

@@ -701,13 +701,12 @@ static int __init prom_setprop(phandle node, const char *nodename,
 }
 
 /* We can't use the standard versions because of relocation headaches. */
-#define isxdigit(c)	(('0' <= (c) && (c) <= '9') \
-			 || ('a' <= (c) && (c) <= 'f') \
-			 || ('A' <= (c) && (c) <= 'F'))
+#define prom_isxdigit(c) \
+	(('0' <= (c) && (c) <= '9') || ('a' <= (c) && (c) <= 'f') || ('A' <= (c) && (c) <= 'F'))
 
-#define isdigit(c)	('0' <= (c) && (c) <= '9')
-#define islower(c)	('a' <= (c) && (c) <= 'z')
-#define toupper(c)	(islower(c) ? ((c) - 'a' + 'A') : (c))
+#define prom_isdigit(c)	('0' <= (c) && (c) <= '9')
+#define prom_islower(c)	('a' <= (c) && (c) <= 'z')
+#define prom_toupper(c)	(prom_islower(c) ? ((c) - 'a' + 'A') : (c))
 
 static unsigned long prom_strtoul(const char *cp, const char **endp)
 {
@@ -716,14 +715,14 @@ static unsigned long prom_strtoul(const char *cp, const char **endp)
 	if (*cp == '0') {
 		base = 8;
 		cp++;
-		if (toupper(*cp) == 'X') {
+		if (prom_toupper(*cp) == 'X') {
 			cp++;
 			base = 16;
 		}
 	}
 
-	while (isxdigit(*cp) &&
-	       (value = isdigit(*cp) ? *cp - '0' : toupper(*cp) - 'A' + 10) < base) {
+	while (prom_isxdigit(*cp) &&
+	       (value = prom_isdigit(*cp) ? *cp - '0' : prom_toupper(*cp) - 'A' + 10) < base) {
 		result = result * base + value;
 		cp++;
 	}