gpio/driver: Sped the gpio_intr_service ISR up by 1.5 uSeconds (+-50% faster).

gpio/driver: Sped the gpio_intr_service ISR up by 1.5 uSeconds (+-50% faster).

Removed as much branching (if statements) from the
gpio_intr_service ISR, as possible and split the while loop into
two. Also forced writing the two status*_w1tc variables only once,
instead of every time after calling the external function hooks.

The measurements below, was done using the following tools:

Toolchain version: crosstool-ng-1.22.0-80-g6c4433a
Compiler version: 5.2.0

Here follows a comparison of the gpio_intr_service ISR's
execution time, using a DS1054 oscilloscope. All the time spent
calling external functions, via the function pointers
gpio_isr_func[gpio_num].fn, were disregarded.

With OPTIMIZATION_FLAGS = -Og, 1.34 uSeconds faster:

3.22 uSec (with this patch)
4.56 uSec (with commit 71c90ac4)

100 - (100 * 4.56 / 3.22) = 42% faster

With OPTIMIZATION_FLAGS = -Os, 1.65 uSeconds faster:

2.89 uSec (with this patch)
4.54 uSec (with commit 71c90ac4)

100 - (100 * 4.54 / 2.89) = 57% faster

Signed-off-by: Konstantin Kondrashov <konstantin@espressif.com>
Merges https://github.com/espressif/esp-idf/pull/2861