checkpatch: fix incorrect camelcase detection on numeric constant

The code fragment below

	int foo(int *array, int index)
	{
		return array[index & 0xFF];
	}

triggers an incorrect camelcase detection by checking a substring of the
hex constant:

	CHECK: Avoid CamelCase: <xFF>
	#3: FILE: test.c:3:
	+	return array[index & 0xFF];

This is caused by passing the whole string "array[index & 0xFF]" to the
inner loop that iterates over a "$Ident" match.  The numeric constant is
not a $Ident as it doesn't start with [A-Za-z_] and should be excluded
from the match.

Similar issue can be detected with other constants like "1uL", "0xffffU".

Force the match to start at word boundary so the $Ident will be properly
checked starting from its first char and the constants will be
filtered-out.

Link: https://lkml.kernel.org/r/20220613100055.77821-1-borneo.antonio@gmail.com
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

scripts/checkpatch.pl

@@ -5721,7 +5721,7 @@ sub process {
 			    $var !~ /^(?:[a-z0-9_]*|[A-Z0-9_]*)?_?[a-z][A-Z](?:_[a-z0-9_]+|_[A-Z0-9_]+)?$/ &&
 #Ignore some three character SI units explicitly, like MiB and KHz
 			    $var !~ /^(?:[a-z_]*?)_?(?:[KMGT]iB|[KMGT]?Hz)(?:_[a-z_]+)?$/) {
-				while ($var =~ m{($Ident)}g) {
+				while ($var =~ m{\b($Ident)}g) {
 					my $word = $1;
 					next if ($word !~ /[A-Z][a-z]|[a-z][A-Z]/);
 					if ($check) {