docs/library: Fix framebuf monochrome 1-bit modes, swapping HLSB/HMSB.

This fix can be demonstrated by the following:

    b = bytearray(32)
    f = framebuf.FrameBuffer(b, 32, 8, framebuf.MONO_HLSB)
    f.pixel(0, 0, 1)
    print('MONO_HLSB', hex(b[0]))

    b = bytearray(32)
    f = framebuf.FrameBuffer(b, 32, 8, framebuf.MONO_HMSB)
    f.pixel(0, 0, 1)
    print('MONO_HMSB', hex(b[0]))

Outcome:

    MONO_HLSB 0x80
    MONO_HMSB 0x1

docs/library/framebuf.rst

@@ -130,7 +130,7 @@ Constants
 
     Monochrome (1-bit) color format
     This defines a mapping where the bits in a byte are horizontally mapped.
-    Each byte occupies 8 horizontal pixels with bit 0 being the leftmost.
+    Each byte occupies 8 horizontal pixels with bit 7 being the leftmost.
     Subsequent bytes appear at successive horizontal locations until the
     rightmost edge is reached. Further bytes are rendered on the next row, one
     pixel lower.
@@ -139,7 +139,7 @@ Constants
 
     Monochrome (1-bit) color format
     This defines a mapping where the bits in a byte are horizontally mapped.
-    Each byte occupies 8 horizontal pixels with bit 7 being the leftmost.
+    Each byte occupies 8 horizontal pixels with bit 0 being the leftmost.
     Subsequent bytes appear at successive horizontal locations until the
     rightmost edge is reached. Further bytes are rendered on the next row, one
     pixel lower.