rdma: fix grammar, formatting, and style in man pages

This patch addresses grammatical errors, overly long section headers,
missing punctuation, and style inconsistencies across all RDMA man
page documentation.

Changes by file:

rdma.8:
  - Fix hyphenation: "non zero" -> "non-zero"
  - Remove article: "a pretty JSON" -> "pretty JSON"
  - Capitalize option description: "output" -> "Output"
  - Add missing period after "monitor"

rdma-dev.8:
  - Split overly long section headers into concise titles + body text
  - Fix semicolon to period and add missing articles
  - Fix possessive: "it's parent" -> "its parent"
  - Add missing article: "specified" -> "the specified"
  - Fix tense: "is previously created" -> "was previously created"
  - Add article: "iproute2 ip command" -> "the iproute2 ip command"
  - Fix verb tense in examples: "Add" -> "Adds", "Delete" -> "Deletes"

rdma-link.8:
  - Split overly long section header
  - Add missing article: "specified" -> "the specified"
  - Add missing periods (2 instances)

rdma-monitor.8:
  - Split awkward section header and reword
  - Add missing period

rdma-resource.8:
  - Add missing article: "specified" -> "the specified"
  - Add missing periods (4 instances)

rdma-statistic.8:
  - Split overly long section header
  - Fix verb form: "are bind" -> "are bound"
  - Add missing periods (7 instances)
  - Fix grammar: "does not exists" -> "it does not exist"
  - Fix plural verb: "that was enabled" -> "that were enabled"

rdma-system.8:
  - Fix plural: "network namespace" -> "network namespaces"
  - Remove duplicate .PP line

The most significant improvements are splitting overly long section
headers across multiple files, fixing missing punctuation in examples,
and correcting various grammatical errors.

No functional changes. All technical content remains accurate.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David Ahern <dsahern@kernel.org>