mfiutil.8/mrsasutil.8: Use Broadcom/LSI consistently

Both tools support controllers from both companies, so document it.

Reviewed by: ziaee (via IRC)
MFC after: immediately
Differential Revision: https://reviews.freebsd.org/D57212

(cherry picked from commit c74645b0c8df1307cb6f13d835012f88883dff3a)