atrf-gpio: accept 'o' as an alias for 'l'

This, while being slightly unsystematic, reduces the risk of confusing
"1" (one) and "l" (lower-case ell).

- tools/atrf-gpio/atben.c (do_atben), tools/atrf-gpio/atusb.c
  (do_atusb): treat 'o' as an alias of 'l'
- tools/atrf-gpio/atrf-gpio.c (usage): list 'o' as alternative for 'l'

tools/atrf-gpio/atben.c

@@ -159,6 +159,7 @@ void do_atben(struct atrf_dsc *dsc, const char *pattern, const char *next)
 			expect |= bit;
 			/* fall through */
 		case 'l':
+		case 'o':
 			read |= bit;
 			/* fall through */
 		case 'z':

tools/atrf-gpio/atrf-gpio.c

@@ -118,11 +118,11 @@ static void usage(const char *name)
 "    addr/value   read and verify one byte from SRAM\n"
 "    #...         comment\n\n"
 "  pattern is a sequence of the following characters:\n"
-"    0 = output a strong 0             1 = output a strong 1\n"
-"    L = pull up, expect to read 0     H = pull up, expect to read 1\n"
-"    l = no pull-up, expect to read 0  h = no pull-up, expect to read 1\n"
-"    Z = pull up, don't read           z = no pull-up, don't read\n"
-"    x = don't care                    . = separator\n"
+"    0 = output a strong 0               1 = output a strong 1\n"
+"    L = pull up, expect to read 0       H = pull up, expect to read 1\n"
+"    l/o = no pull-up, expect to read 0  h = no pull-up, expect to read 1\n"
+"    Z = pull up, don't read             z = no pull-up, don't read\n"
+"    x = don't care                      . = separator\n"
     , name, atrf_default_driver_name());
 	exit(1);
 }
@@ -134,7 +134,7 @@ static void usage(const char *name)
  * H	pull-up, read 1
  * L	pull-up, read 0
  * h	no pull-up, read 1
- * l	no pull-up, read 0
+ * l/o	no pull-up, read 0
  * Z	pull-up, don't read
  * z	no pull-up, don't read
  * x	don't care
@@ -168,7 +168,7 @@ int main(int argc, char *const *argv)
 		if (reg_op(NULL, argv[i], 0))
 			continue;
 		for (s = argv[i]; *s; s++)
-			if (!strchr("01HLhlZzx.", *s))
+			if (!strchr("01HLhloZzx.", *s))
 				fprintf(stderr,
 				    "invalid configuration '%c' in \"%s\"\n",
 				    *s, argv[i]);

tools/atrf-gpio/atusb.c

@@ -160,6 +160,7 @@ void do_atusb(struct atrf_dsc *dsc, const char *pattern, const char *next)
 			expect[port] |= bit;
 			/* fall through */
 		case 'l':
+		case 'o':
 			read[port] |= bit;
 			/* fall through */
 		case 'z':