PX4/NuttX branch test: master

NuttX:
 - https://github.com/PX4-NuttX/nuttx/tree/master
 - PX4/NuttX@48760b2

Changes from PX4/NuttX (PX4/NuttX@423371c) in current PX4/master (72a4494)
PX4/NuttX@423371c...48760b2

48760b2 (HEAD, origin/master) Merged in masayuki2009/nuttx.nuttx/improve_gs2200m_performance (pull request #931)
55026f2 arch/arm/src/am335x:  Add clock module registers definition.  Switch to DMTIMER1 for systick.
03fe07c Merged in bkueng/nuttx/uart_invert_ioctl_continued (pull request #930)
093f98c arch/arm/src/imxrt/imxrt_usdhc.c:  Implements SDIO and Multi-card support for i.MX RT.
1395938 arch/arm/src/stm32f7/stm32_serial.c:  This adds the ability to invert and swap RX/TX on STM32F7 UARTs.  I added the TIOCGINVERT as well to reserve the IOCTL number, but did not implement it. This is the same as for TIOCGSINGLEWIRE.
118d0f8 Trivial updates to last PR for minor issues reported by tools/nxstyle.
55a4029 Merged in alinjerpelea/nuttx (pull request #928)
7815c3a Merged in masayuki2009/nuttx.nuttx/tiva_with_qemu (pull request #927)
b6e7812 Merged in masayuki2009/nuttx.nuttx/fix_gs2200m (pull request #926)
1346f29 net/: Fix alignment and spacing problems found by tools/nxstyle.

Apps:
 - https://github.com/PX4/NuttX-apps/tree/master
 - PX4/NuttX-apps@c131733

Changes from PX4/NuttX-apps (PX4/NuttX-apps@7db2a35) in current PX4/master (72a4494)
PX4/NuttX-apps@7db2a35...c131733

c131733 (HEAD -> master, origin/master) Merged in masayuki2009/nuttx.apps/mp3_on_webserver (pull request #180)
b12b61d Merged in masayuki2009/nuttx.apps/fix_webserver (pull request #179)
ee8af2a Fix warnings found in build testing.
334b450 wireless/gs2200m/gs2200m_main.c:  Fix a warning about an uninitialized return value found in build testing.
18a8032 examples/vl53l1x:  Remove.  The driver does not compile.
94ac7dc examples/vl53l1x:  Add VL53L1X example demo.
27766d7 Merged in masayuki2009/nuttx.apps/fix_apps_industry (pull request #178)
d2f3ad9 Merged in masayuki2009/nuttx.apps/wireless_gs2200m (pull request #177)
2c8e349 Merged in masayuki2009/nuttx.apps/add_system_gs2200m (pull request #176)
6561573 industry/abnt_codi, include/industry/abnt_code.h, examples.abntcodi:  Adds support for ABNT CODI library.  This is an energy meter protocol used in Brazil.