update PWM test for 4.14 kernel udev paths

pytest now passes all tests OK on 4.14.0-rc7-ti-r6 as non-root user:

debian@beaglebone:~/ssh/adafruit-beaglebone-io-python/test$ python -m pytest
======== test session starts =============
platform linux2 -- Python 2.7.13, pytest-3.2.3, py-1.4.34, pluggy-0.4.0
rootdir: /home/debian/ssh/adafruit-beaglebone-io-python, inifile:
collected 58 items

test_adc.py ......
test_gpio_input.py ..
test_gpio_output.py ......
test_gpio_setup.py ..........
test_led.py ..
test_pwm_setup.py ...........................
test_spi.py ..
test_uart.py ...

======== 58 passed in 13.30 seconds ========

debian@beaglebone:~$ sudo /opt/scripts/tools/version.sh
git:/opt/scripts/:[6c2688b0be448b7bb9ca18849b430d496a84acb4]
eeprom:[A335BNLT000C3014BBBK1316]
model:[TI_AM335x_BeagleBone_Black]
dogtag:[BeagleBoard.org Debian Image 2017-10-17]
bootloader:[microSD-(push-button)]:[/dev/mmcblk0]:[U-Boot 2017.09-00002-g0f3f1c7907]
bootloader:[eMMC-(default)]:[/dev/mmcblk1]:[U-Boot 2017.09-rc2-00002-g84a7f2]
kernel:[4.14.0-rc7-ti-r6]
nodejs:[v6.11.5]
uboot_overlay_options:[enable_uboot_overlays=1]
uboot_overlay_options:[uboot_overlay_pru=/lib/firmware/AM335X-PRU-RPROC-4-4-TI-00A0.dtbo]
uboot_overlay_options:[enable_uboot_cape_universal=1]
pkg:[bb-cape-overlays]:[4.4.20171027.1-0rcnee1~stretch+20171027]
pkg:[bb-wl18xx-firmware]:[1.20170829-0rcnee1~stretch+20170829]
pkg:[firmware-ti-connectivity]:[20170823-1rcnee0~stretch+20170830]

Author: pdp7

test/test_pwm_setup.py

@@ -18,7 +18,7 @@ def get_pwm_dir():
         # .pwm or .ehrpwm, etc.
         results = glob.glob(
             "/sys/devices/platform/ocp/48302000.*/" +
-            "48302200.*/pwm/pwmchip?/pwm0")
+            "48302200.*/pwm/pwmchip?/pwm*")
         # We expect that there will be a result (a directory fitting
         # our path exists) so test that with an assertion.
         assert len(results) > 0