Report SPI frequency accurately on Espressif

[dhalbert]

• Fixes SPI Frequency change limits not reflected on Espressif port #7593.

Test on Metro ESP32-S2:

>>> import board
>>> s = board.SPI()
>>> s.frequency
250000
>>> s.try_lock()
True
>>> s.configure(baudrate=10)
>>> s.frequency
152
>>> s.configure(baudrate=100)
>>> s.frequency
152
>>> s.configure(baudrate=1000)
>>> s.frequency
1000
>>> s.configure(baudrate=100000)
>>> s.frequency
100000
>>> s.configure(baudrate=1000000)
>>> s.frequency
1000000
>>> s.configure(baudrate=10000000)
>>> s.frequency
10000000
>>> s.configure(baudrate=100000000)
>>> s.frequency
80000000
>>> s.configure(baudrate=123456)
>>> s.frequency
123456
>>> s.configure(baudrate=123888)
>>> s.frequency
123839

[gamblor21]

Tested on a TinyS2 and works fine. Thanks for the fix!