[PC-656] Mention PF1550 in Portenta H7 features

[aliphys]

What This PR Changes

• The PF1550 is a two in one voltage regulator and battery charging IC.
• Also, it can be configured via the https://github.com/arduino-libraries/Arduino_PF1550 library
• Added this in the features section so customers can more easily see this unique feature

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[jcarolinares]

Thanks for the change suggestion @aliphys we will wait until @canchebagur do the changes at Portenta H7 family to see if it makes sense :)

[aliphys]

@jcarolinares Can we merge this now? :)